Top 4 Ways You’re Wasting Gas When You Think You’re Saving It
May 22nd, 2007 | by Brian Carr |With the price of gasoline up over 40% since the beginning of the year, many people are trying to find new ways to save money at the pump.
While many of these ideas are useful and worth the extra effort - i.e. adjusting your commuting time, cleaning out your car’s trunk, turning off your car at long stop lights - many driving habits that people think will help them save gas or money are actually causing them to waste both.
So on that note, here are the top four ways people think they’re saving money and/or gas when they’re actually not:
- Driving across town to save a nickel on a gallon of gas. With gas prices at record highs, many people are doing everything they can to reduce the amount of money they spend at the pump. One of the more popular ways people are doing this is by using sites like Gasbuddy.com to find the cheapest gas stations in their zip code. Unfortunately, many of these same people are driving long distances to save a couple of pennies on a gallon of gas - meaning they’re probably burning up the amount of money they save by using extra gas to go to an out of the way station.
- Driving on the highway with their windows down to avoid using the air conditioner. We’ve become accustomed to thinking that our car’s AC is the biggest drain on our car’s gas mileage. While using it will reduce your gas mileage, there are many instances where using your AC instead of rolling down the windows will actually be better for your car’s gas mileage. One of the biggest drains on your car’s gas mileage is aerodynamic drag - something that is exacerbated by rolling down the windows. If you’re going to drive on the highway, go ahead and turn on your AC and keep the windows up!
- Driving with their truck’s tailgate down. Many people believe that driving with their truck’s tailgate down will improve gas mileage. Unfortunately, the opposite is actually true. When a truck’s tailgate is up, a “protective air bubble” will form in the bed area which actually makes the truck a little more aerodynamic; when the tailgate is down, this bubble disappears and gas mileage gets worse.
- Accelerating extremely slowly. Many people think that the slower they accelerate, the better gas mileage they’re going to get. Unfortunately, extremely slow acceleration can bog down your engine and make it run less efficiently - thus wasting fuel. So, instead of slamming the accelerator to the floor or barely even touching it, try and find a nice happy medium so you can achieve a moderate acceleration.
So, if you’ve been doing the aforementioned items, I certainly can’t fault you for trying to save gas and money, however, there’s a reason why you haven’t seen much of a savings - these ideas just don’t work.
98 Responses to “Top 4 Ways You’re Wasting Gas When You Think You’re Saving It”
By Jesse on May 23, 2007 | Reply
yeah… the A/C one is totally wrong. I’ve done tests with my vehicle and the difference is dramatic. The A/C gobbles up gas. Windows don’t. If you need more proof see the mythbusters episode where they test that exact theory.
By sakanagai on May 23, 2007 | Reply
You forgot “Drive the speed limit”.
Many people have heard that for each 5 mph over the speed limit you go, you add 20 cents per gallon. The gas mileage of a vehicle is not dependent on the speed limit of the roads, rather the speed of the vehicle. If you go 60 mph, you use just as much fuel in a 55mph zone as a 65 mph zone. Most cars reach peak efficiency at around 60 mph, while trucks and SUVs reach theirs around 85 mph. It’s still wise to experiment with your vehicle to find your peak as opposed to guessing or living in ignorance.
By Obbop on May 23, 2007 | Reply
“Most cars reach peak efficiency at around 60 mph, while trucks and SUVs reach theirs around 85 mph.”
With hands clutched tightly, forming “fists of rage,” I, the Mighty Obbop, star of neither screen nor stage and a dweller of http://www.bannination.com, screams to the world, “Huh?.”
How oh how can any logically-thinking humanoid dare to proclaim that “peak efficiency” occurs at a speed offering less of those little mpg things than driving at a lower speed?
Over the decades, a multitude of folks with better minds than I (this includes sundry cartoon characters) have asserted that various algorithms (Al Gore rhythms?) indicate the most fuel efficient speed is with 45 of those little mph thingys.
If thou disagreeth meet me at the bike racks after school.
By Brian Carr on May 23, 2007 | Reply
Jesse - that’s not entirely true:
http://en.wikipedia.org/wiki/MythBusters_%28season_2%29#AC_vs._Windows_Down
http://en.wikipedia.org/wiki/MythBusters_%28season_3%29#AC_vs._Windows_Down
Like everything else, there are a lot of variables, but it seems to be show that the faster you’re driving the more having your windows down saps your car’s gas mileage.
By Brian on May 23, 2007 | Reply
“the most fuel efficient speed is with 45 of those little mph thingys.”
Engine effiency is based on engine load and RPM. Assuming a flat road and constant speed, you get a speed/effiency curve for each gear the car can be in. On a normally aspirated car, this usually looks like a bell curve, with one maxima. So, for any gear, you have a most effient speed, with the higest gear usually being the most efficient overall. For some cars its 45, others 60, and some even higher. If you have a forced induction car, e.g. turbo or supercharger, the car may have more than one peak effiency point.
By rubens hakkamacher on May 23, 2007 | Reply
Fuel efficiency relates to your rpms.
Period.
The lower you keep your revs, you WILL save gas.
Coasting when possible is good.
Keeping your momentum going is good.
/ gets 33mpg in a car rated for 28
By sakanagai on May 23, 2007 | Reply
Obbop,
Geez. I didn’t mean to start a schoolyard fight (?) or anything. I was just commenting that there wasn’t some sort of magical forcefield that deducts fuel efficiency if you exceed the posted speed limit.
Perhaps the term “peak efficiency” was used out of place, but crikey. IT was the term that my team used in GM’s Challenge-X (that alternative-fuel SUV project), and our control truck (market engine) peaked at 77 mph in the simulation program.
By John on May 23, 2007 | Reply
rubens hakkamacher: BS, BS, BS. RPMs have almost nothing to do with the amount of gas your using, its almost completely dependent on how far your gas petal is pushed down. When you let go of the gas petal, even if your RPMS are still at 3000 you will use NO gas (on a fuel injected engine) because the wheels are keeping your engine turned over and you don’t need gas.
BTW the you lose efficiency going over the speed limit has some truth, in so much that going over the speed limit greatly increases your chances of needing to suddenly brake. Generally speed limits are set based on such things.
By m4yh3m on May 23, 2007 | Reply
The best way to save gas — keep it under 2,000 RPM. Want to see where your gas is going? To hell with the speedometer. Watch your tachometer. No matter how fast you go (but always obey the speed limit), keep it under 2,000 RPM and you’ll save more gas. Some cars can go up to 80 MPH (my vehicle, for instance) while staying right on 2,000. I know other people who can only do 65 MPH while staying at 2,000. Either way, you’ll be saving gas. Higher RPMs means your engine is burning much more gas to to stay at that constant MPH. Find out how fast you can legally go while keeping it under 2000, or between 1500 - 2000, and do that speed. If it means leaving a little earlier to get there on time, wouldn’t it be worth it considering the amount of money you’d be saving?
By Chris on May 23, 2007 | Reply
As they stated on the aforementioned episode of Mythbusters, the amount of drag increases with the cube of the speed, which has to be taken in to account along with the horsepower curve of the engine to determine the optimum speed.
By Rob on May 23, 2007 | Reply
John
“Generally speed limits are set based on such things.”
Um… no. Generally speed limits are set by arbitrary political factors and population density formulas, not engineering, physics, or other such ’science.’ There are cases where speed limits are set appropriately, however those are mostly entirely by accident.
You are correct in your assertion that heavy braking (typically followed by heavy acceleration) are the true bane of gas efficiency. Next time you’re in a parking lot or stop light, check out the rims of the vehicle s near you. Vehicles with lots of black brake dust on the front wheels (for awd and fwd) are the most egregious offenders. Leave some space, use your transmission for slowing yourself down, your brakes are there to stop you.
Of course, the prevalence of automatic transmissions makes all of this moot as most drivers are mindless drones simply pointing and shooting their way too and from work.
By Scott on May 23, 2007 | Reply
My F-250 gets it’s best mpg when it’s loaded to the gills with family and luggage and hauling butt at 80mph. I’ve also discovered that some vehicles get better mpg on gas from a particular station. My truck likes Shell and Texaco, while my car seems to like the local station called Zoom’s, which gets its gas from a local Giant refinery. Over a few years, I’ve noticed a 2-3 mpg difference when I buy my gas at the right place.
I’ve tried the smooth and gradual acceleration, driving the speed limit, etc., and it really never made a noticeable difference, other than having other drivers flip me the bird.
By Conundrum on May 23, 2007 | Reply
Although you may spend a few extra cents going to the cheapest gas station in the area, I would suggest that we all do just that. If we continue to reward gas companies with our business just because they are closer and ‘convenient’, in the long run we are admitting that we don’t mind paying higher prices.
Use gasbuddy.com and actively avoid retailers that are in the top 10%. Make a point to drive accross town. They lose the business from the snacks, cigarettes and other purchases as well. Do your best to reward those who keep their prices low.
By Kidder on May 23, 2007 | Reply
I think a lot of people forget that the gas pedal isn’t the only pedal that figures into the mpg equation, but the brake pedal also plays a role. If you find yourself constantly having to firmly hit the brakes, you’re wasting the momentum that was just built up by your engine, while burning gas. For instance, if you accelerate from 0-60 in 7 seconds, then find that you have to hit your brakes hard to slow down for a car in front of you, you just wasted a lot of the gas that you burned to get you up to that speed to begin with.
Like everything else in life, moderation is key. Use the accelerator moderately, use the brake pedal moderately, and find a happy balance betwee them.
By dave c on May 23, 2007 | Reply
i have a 2002 hyundai elantra. if i set cruise control at 60MPH with AC on, i get 32MPG. at 75MPH with the AC on, i get 28MPG.
at 45MPH with the AC on, i get 27, unless i get out of OD. i set the car in third gear and it actually gets a bit better mileage. the trick is to keep it between 2000 and 2700 RPM.
but that’s just my type of car.
By Pea Tear Griffin on May 23, 2007 | Reply
To hell with the speedometer. Watch your tachometer. No matter how fast you go (but always obey the speed limit), keep it under 2,000 RPM and you’ll save more gas.
Yeah! To hell with science and the physics that govern internal combustion engines…with all their variables like valve timing, etc, that govern the RPM at which your engine operates most efficiently! YEAH!!!
Hey Conundrum…what if the gas station that sells cheap gas jacks up their cigarette and beer prices? THEN what do you do?
By roofus on May 23, 2007 | Reply
rubens - it’s about injector pulse width or throttle plate twist depending on whether you’re injected or not.
when I am going 145mph on the freeway my mileage is less than 6.0, but my car wont bother calculating it lower than that
By Terry on May 23, 2007 | Reply
Gas mileage is actually simple, but it’s based on complex issues.
Other posts have hit on some of the issues, but it involves many factors.
Are the tires inflated properly?
Type of tires?
Is the vehicle body dirty?
Engine horsepower?
Weight of vehicle?
Weight of cargo?
Fuel/air mixture properties?
Cylinder(s) and combustion properties?
Aerodynamics?
Vehicle size?
Gear ratios?
Drivetrain components?
Transmission type?
etc, etc….
All things being equal, a drop of 90 octane gas has a set amount of energy within it to move a respective mass, which no amount of wishing can change, period.
I’d also note that all gasoline is initially created equal, the difference arises with which retailer has what detergents or other additives put in it to disginguish themselves from the others. Additives may help keep your engine/fuel system cleaner, but do nothing to create energy.
Gas mileage is bound to vary depending on all the above and then some.
I would generally agree that the lower the RPM’s mixed with the higher gear ratio, lower drag coefficent and lower vehicle weight will yield the best mileage.
I would also agree with one of the posters that 45mph is the optimum
speed for many vehicles, however unpracticle that may sound in some circumstances. Most people don’t have a Ferrari. And that utilizing coasting techniques with a manual transmission and minimal braking also helps.
Anyone that says different, either isn’t being truthful, or isn’t/can’t test all the various factors in total precisely enough.
By tkid on May 23, 2007 | Reply
just walk, it will save you a crap-ton
By JWC on May 23, 2007 | Reply
Some of you guys have a lot to learn about internal combustion engines and thermodynamics. Your ultimate gas mileage is, as John sort of stated in post #8, determined by your throttle position and speed. How much gas are you using v/s how far you’re going. That’s all there is to it. RPMs are a simply a byproduct of throttle position, engine load, and gearing. RPMs alone are NOT a good indicator of fuel economy. If you’ve got your throttle wide open, but you’re trying to chug up a hill in your top gear staying under 2000 RPM, do you really think you’re saving gas? Hell no, you’re drinking it like it’s going out of style
If you really want a good indicator of fuel economy, install a vacuum gauge on your dash.
By Strings on May 23, 2007 | Reply
Driving across town to save a nickel on a gallon of gas.
I partially agree/disagree with this.
Going across town just to get gas that’s cheaper isn’t worth it.
However, combining the trip with other errands that are also across town will make it prudent.
Such as getting gas at Costco when you shop there.
By Downbound on May 23, 2007 | Reply
Gas, what’s this gas you speak of? Mmmm Bio-Diesel.
By gordon on May 23, 2007 | Reply
I do AC on the highway and windows down on country roads. One thing people always mess up on is that you should drive the route that allows the most constant motion. My commute to work is 23 miles by highway and 20 by roads but on the highway I set my cruise control and go. On the regular roads I would be stopping and starting.
By jcaus on May 23, 2007 | Reply
So if the RPM theory is true, then my 1 ton Civic at 3,000 RPMs at 65mph is less efficient than my 2.5 Ton F150 at 1500 RPMs at 65mph. That’s good to know!
/had no idea so many people failed High School Physics.
By Tim O on May 23, 2007 | Reply
buy a hybrid. We just got a new Toyota Prius–first tank of gas (around-town driving) was 58.2 MPG. And it is a nice car, with more room inside than would appear from the outside.
By Alex on May 23, 2007 | Reply
I don’t use gas buddy, but being on the border of NY with NJ, I always drive down to Jersey to get my gas, it’s always at least 15-20 pennies per gallon cheaper there.
By Goodboyfine on May 23, 2007 | Reply
Driving across town to save a nickel? It may not make sense in the short term, but it makes lots of sense in the long term. It is the only weapon available in the fight against greedy oil companies. Withhold business and shop the best price.
By One Bullet Barney on May 23, 2007 | Reply
Why worry about it, my 7 liter engine is going to suck down gas either way, might as well enjoy it. beside al gore created the internet, he will solve global warming in his sleep while hunting down oshama
By Brandon on May 23, 2007 | Reply
Like people said above, with manual transmission coasting down a hill or any type of incline is good for gas. I’m not sure if this is true or not, but if your car is turbocharged, you lose mpg when you start boosting, it’s something I’ve noticed but don’t know if it’s true.
By Falk on May 23, 2007 | Reply
Chris speaks truth in #10. The force of drag on any object is D = ½*r*Cdp*A*V², where r, Cdp and A are constants (density of air, coefficient of drag, cross-section area) and V is velocity. This means that drag is a function of V² and since power is P=F*V, power is a function of V³.
It may be true that engines are more efficient at a specific RPM (I don’t know), but that doesn’t really relate to velocity because you could always change the gearing, and anyway the difference is insignificant compared to that V³ factor.
By ToyotaTs on May 23, 2007 | Reply
We just bought a 2007 Toyota Prius (top of the line) and a 2007 Toyota Yaris Liftback (manual). Even if you get the Prius entry level (or thereabouts), the smarter buy is the Yaris (or even the Corolla). Once you start computing the actual mileage off the actual gas for your Prius (as opposed to the in-dash MPG display), you will find you drop down around 45-47 mpg. The $10K+ cheaper Yaris will buy alot of gas to offset the 5mpg difference of the Prius.
However, if you are in chronic stop-and-go traffic in your morning/afternoon commute, then the Prius will deliver more like it should (50-60 mpg).
Tt
By No1_vern on May 23, 2007 | Reply
IF you want to save cost by using less gasoline, SLOW DOWN For ever MPH above 60 wind resistance increases proportionately, and gas economy suffers.
Traveling at 55 down to about 40 give you the highest bang per buck. Slower and RPMs produced by the engine has to work to pull the weight of the car, faster and the engine works harder to overcome wind resistance.
OF course if you want to get serious about saving money and can do so, ditch the car and buy a bicycle. The gas stations will shake their fists at you while you become healthier.
By Espot on May 23, 2007 | Reply
Another way to get better mileage is to buy a car with continuously variable transmission (CVT). This transmission keeps the engine at it’s most fuel efficient RPM, and varies the gear ratio in order to accelerate (although there aren’t actual gears in a CVT).
By Mike on May 23, 2007 | Reply
“So if the RPM theory is true, then my 1 ton Civic at 3,000 RPMs at 65mph is less efficient than my 2.5 Ton F150 at 1500 RPMs at 65mph. That’s good to know!”
I think the “RPM theory” being referred to is talking about the gas millage relative to a single vehicle. Ergo, your Civic will use less gas at 1500 RPMs than at 3000 RPMs.
I guess you didn’t learn much about relativity in physics?
By Clocker on May 23, 2007 | Reply
I live in South Florida, where you need the A/C year round. I just spent six months with no A/C in the car (busted compressor clutch), and therefore drove around with the windows down. My average MPG went from 24 to 26 up to 27 to 30. Once the A/C was repaired, it dropped right back down. I figured I saved enough on gas over the six months to pay for the repair…
By cptvitamin on May 23, 2007 | Reply
@ToyotaTs
Funny, I have been driving a 2006 toyota prius for just about a year now and have kept an accurate record (computed, not reported by vehicle) of fuel consumption and I find the opposite is true. When I drive long winding back roads where I can maintain a constant speed of around 35-50 MPH I get between 50-60 MPG. When I do lots of local driving, stop and go, I get as low as 40. I find the biggest factor on fuel efficiency with the Prius is outside temperature. I average 55 MPG in warm weather (50-80 F) and 45 MPG in cold.
By Anonymous on May 23, 2007 | Reply
my bicycle seems to get NAN miles per gallon. but it does sometimes take its toll in other ways…
By Brains on May 23, 2007 | Reply
I’ll have you know, I’m burning up the extra fuel all you tree hugger hybrid yuppie pukes are “saving”
Gas prices have nothing to do with supply and demand, they instead have everything to do with political policy and greed.
I drive two cars. One is a 500 horsepower toy, and gets 16mpg around town (~24 on the freeway). The other is a 425 horsepower land barge, and it also gets around 16mpg (20 on the freeway). That yuppie hybrid group can kiss my ass, stay in the right lane and let me pass
By W. Andrew Loe III on May 23, 2007 | Reply
@32
Not to mention the insane amount of pollution required to create the batteries in the Prius.
Prius are not good for the environment, they do get some pretty good fuel economy but you would need to drive it for 15 years before that small increase in fuel economy is going to offset what you created buy having the battery manufactured.
Fuel economy isn’t everything.
By Awesimo on May 23, 2007 | Reply
You can save $ by putting regular in your Civic, Explororer, Audi, etc. Save the ULTRA and Super grade gas for the H2’s, Vipers, and Haulers.
You can also leave your car running with the windows down and doors unlocked while you spend 20 minutes in the grocery store
I wonder how much of the country’s fuel is being wasted in traffic jams and worker’s air conditioning
By dfgdh on May 23, 2007 | Reply
Contact your local delegate to widen highways and add Red light sensors to change lights, that’ll save $
By Ray on May 23, 2007 | Reply
Mythbusters did tests on the AC vs. open windows and at 50 MPH the Ac lost.
By Rob on May 23, 2007 | Reply
It’s been eluded to, & that math formula is still giving me a head ache, but ‘pushing the air’ in front of your car is the greatest cost of running your car beyond, even considering peak performance at a certain rpm.
think about it.
2000 rpms at 20 miles per hour = less effort for your car than
2000 rpms at 60 miles per hour.
When your car is traveling at constant velocity, the net force on it must be zero. (when your car is standing still, the engine isn’t forcing it to move forward and the air isn’t forcing it to move backward) Since it needs a forward force from the ground (your engine attached to the tires), something must be exerting a backward force on it. On a level road, that something can only be air resistance.
if you want to see what your car has to put up with try sticking your hand out the window at both speeds & see if you can ‘feel’ what your cars engine is putting up with.
That said, 60 mph, should always yeild better MPG than 80.
this is also why your car has a ‘top speed.’ eventually, the motor doesn’t have enough power to overcome the amount of air resistance (backward force). ie: your engine’s ability to accelerate is = to the air resistance coming at it.
I’ve heard the ‘formula’ described this way:
the ‘force’ of the air on your car doubles exponentially as you accellerate.
here’s an example of the backward force of the air (in pounds) against a corvette at various speeds.
You can easily see that
(mph) 15 30 60 90 120 150
Force 3.60 14.5 58.0 130 232 362
(the ‘force’ can also be looked at as a measurement of how much more ‘air resistance’ there is at each of the speeds.)
of course you need to have properly inflated tires, and a well maintained engine, but you can clearly see here, that as you increase speed, you severly increase in effort that the engine must exert. The only way your car exerts more effort, is by using more gas!
By 427Galaxie on May 23, 2007 | Reply
Engines are most efficient steady-state at their torque peak, where BSFC (brake specific fuel consumption) is at it’s lowest. Match the torque peak of an engine to a vehicle’s most used cruise speed via proper gearing, and you have an optimized combination. The single variable with the greatest effect on fuel economy is your right foot– the greater the throttle opening, the more air will flow into the engine, and a commensurate amount of fuel will need to be mixed to insure proper combustion and the longevity of the engine.
As far as air drag and the 45 mph magic number are concerned, it’s a ’sweet spot’ where most vehicles experience considerably less drag than at higher speeds, and so require little power (hence fuel) to travel. Test it yourself… stick your hand out the window at 45mph and hold it in place. Try again at 55, 65, and 75 mph. The force required for you to hold your hand in place correlates to the amount of force required for your vehicle to push it’s way through the air.
By ToyotaTs on May 23, 2007 | Reply
@cptvitamin (37)
Yes, your driving in the 30mph and lower range definately puts you in the range to be utilizing the electric power more…especially if you accelerate fairly slowly.
Our commute is always 45mpg or so, so we end up getting about 45 to 50 mpg depending how much stop-n-go and 25mph (or is it 23mph the cutoff?) or less traffic we get. We did notice a few mpg drop with the cold weather too…which from what I have read is about the same for most cars.
@Loe III (40)
One of the universities did a study of the Prius emissions and said it was very, very environmentally friendly so that probably easily offsets any battery making process and disposal. There’s pollution from petroleum product manufacture too, no? Even with the by-product down-level chain…
Tt
By ToyotaTs on May 23, 2007 | Reply
@Brains (39):
“politcal policy and greed”
Agree for the most part. Would rather reward Toyota with a few purchases of vehicles utilizing technology heading in the right direction than reward big oil, it cronies, and OPEC and crew.
Just cut us puny vehicles some slack in your humongous and power oriented vehicles, okay?
Tt
By vDub on May 23, 2007 | Reply
My car doesn’t use any gas! (It’s a VW Jetta diesel.) I’m averaging about 34MPG mixed driving. Now that diesel prices are lower than regular gas, it’s win-win. The only down-side is the oil changes are more expensive because it requires a special VW-approved synthetic grade.
By Mike on May 23, 2007 | Reply
The A/C vs. wind drag one is typically not true, although it probably would be true for certain car designs where the windows are huge scoops, T-tops, and some convertibles (mostly where air doesn’t flow past the window instead of into it). The reality is that A/C becomes more efficient the faster you go (as more airflow increases it’s radiant cooling capacity) and drag increases at velocity-squared (so doubling your velocity quadruples your drag), but drag is very low in comparison to A/C drain to begin with. Another way to look at this foundation is: if you were sitting still, is A/C or open windows more fuel-efficient? Clearly open windows.
What this all means is that there is a point where the A/C efficiency increasing crosses the line corresponding to drag (or speed efficiency) decreases, and it becomes better to use the A/C. For most cars, though, this point is probably way beyond the speed limit.
My Volvo has a readout that shows me the MPG updated every couple of seconds, and I have tested A/C vs. open windows in a variety of conditions, and open windows universally wins, even at 70+ mph. I am my own Mythbuster…
By Big Tony on May 23, 2007 | Reply
I don’t really car about this whole gas thing since there is no real way to avoid it. I would like to say that one of “Rob’s” posts was absolutely perfect. I wish more people would learn to simply take their foot off the accelerator instead of constantly braking all the time. Unless there is a reason to come to a sudden or complete stop or reduce your speed drastically, you really shouldn’t need to use your brakes that much. I hate people who constantly tap on their brakes while they are driving. People need to learn to drive with the cars engine not with its brakes.
By Ross on May 23, 2007 | Reply
The Mythbusters guys should never be cited as an authority on anything. What they do on their show is ‘entertainment science’.
(i do enjoy the show but their conclusions should never be taken seriously)
By EBounding on May 23, 2007 | Reply
I have a 2007 Civic EX. Setting the cruise to 60 MPH with the windows down a quarter of the way gets me around 48MPG (rated at 40). Cruising at 70, I get between 35-40MPG. 70+MPH I get 30MPG. I’ll have to try with the A/C on low.
Oh, and 48MPG sounds good, but I only get 24MPG in heavy traffic. So it all boils down to how, when and where you drive.
By Andrew Norris on May 23, 2007 | Reply
These are all just ideas, never actually investigated or facts as claimed.
I think this was written up in 10 minutes (or less).
I know for a fact going light on the accelerator saves A LOT of fuel.
By John on May 23, 2007 | Reply
“the most fuel efficient speed is with 45 of those little mph thingys.”
I have tested this in my car, and I get the best efficiency (at reasonable speeds, I’m not going to do 15 Mph on a highway) at 85Mph in 6th. I get about a 4 Mpg boost!
By Andrew Norris on May 23, 2007 | Reply
The gasbuddy one - maybe - we all know about it. And we all know some people can be that stupid - but how many actually are? It’s unknown basically until a test is done.
By Brian Carr on May 23, 2007 | Reply
Andrew - go back and re-read the article. Yes, taking it light on the accelerator does save a lot of fuel, but taking it so easy that you bog down the engine also wastes fuel.
By Craig Mack on May 23, 2007 | Reply
Mythbusters has disproved both the A/C vs windows myth as well as the truck tailgate myth. Both are untrue. To really save gas, tell these single women to stop driving their obnoxious children around in a Ford Expedition!
By Chris Bergeron on May 23, 2007 | Reply
John - rubens hakkamacher is correct.
As a vehicle coasts (and doesn’t burn fuel as you said, which is also wrong), it creates unnecessary drag on the car via the drivetrain. If what you’re saying about EFI cars not burning gas while the car runs at 3000 RPMs is true, then the momentum of the car is being decreased by having to turn over the engine.
I have both an EFI car, and a naturally aspirated one; the naturally aspirated car goes MUCH FARTHER when coasting. The EFI car can’t coast nearly as far, and actually LOSES SPEED EVEN DOWNHILLS.
That loss of momentum results in much higher fuel consumption, because the engine will have to work harder (at higher RPMs I might add) to get the car back to the speed it was cruising at.
Therefore, lower RPMs save fuel.
By country mouse on May 23, 2007 | Reply
the energy cost of air conditioning is worth it for one very simple reason.
Safety.
if you are cool and comfortable you’re able to think much more clearly and react to road conditions than you would if you had a loud roar of hot air blowing over you. I don’t know about you but I would prefer to avoid any potential accidents or unpleasant events (i.e. road rage) and therefore I’ll use air-conditioning regardless of the energy costs.
A secondary reason is noise. if you have passengers in the car or like to play your radio, loud air movement (anything over 25 miles an hour) means you have to scream at your passenger in order to be heard. Under the same conditions, your radio is playing much louder than normal which further obscures your ability to hear any acoustic warnings such as emergency vehicles until they are right on top of you.
Play it safe. Use air-conditioning and drive sanely
By butcher99 on May 23, 2007 | Reply
In tests just done at a university (forget which one) they found that neither the AC nor windows down cause any more or less fuel useage.
By Jason on May 23, 2007 | Reply
@Brains
Apparently, you have none.
By Josh on May 24, 2007 | Reply
OK….here’s the deal with the engine RPM/fuel injection story. You can calculate gas mileage very simply if you have a few known constants. One is the flow rate of a single fuel injector. The second is the number of fuel injectors (usually one per cylinder but larger engines may have two). Fuel injectors do not vary how fast fuel flows out of them. That is determined by your fuel pump, fuel pressure regulator, and flow rate of the injector, which remains constant. What they do vary is how long they are spraying fuel into a cylinder during the intake stroke (pulse width modulation) and how often they have to do it (frequency/RPM). The longer the pulse and the more often the pulse occurs, the more fuel that is used. A single cylinder four stroke engine will inject fuel once per two revolutions. A four cylinder engine will inject fuel four times per two revolutions, and so on. It appears that the higher the revolutions, the more fuel that is used. This is true if the injector open duration is long. Under load or acceleration this is likely to be the case. However, under normal operation the injection period is likely to be shorter due to the higher frequency of injections (less time to spray in fuel when the valves are closing faster). To calculate gas mileage then you simply need to know how fast you are going and how much gas you are using per second (and of course do some conversions and math). When you take your foot off of the gas and the engine is coasting with the speed of the car, it is not using any gas! The fuel injectors shut off the whole time the car is pushing the engine. If you drive a manual transmission you may be tempted to release the engine from the transmission to bring down the revs. DO NOT DO THIS! What you are doing when you coast in neutral is making the engine idle which burns gas to keep it running. Carburetors never shut off the gas which is why you may get back-firing when you let off the gas and the carb isn’t tuned. It is true that you want to drive at the RPM where your engine is most efficient. This is where the engine makes the most power with the least amount of gas but is determined by many outside factors like loading, temperature, gas quality, atmospheric pressure, etc.. Higher speeds = more loading. There is no cookie cutter speed for every single vehicle to adhere to to obtain maximum efficiency. Finding that speed without a real-time miles per gallon calculator is not trivial. Throw in some extra cargo and people and you’ve just changed everything. I for one, am for car manufacturers being required to install real-time MPG calculators on every vehicle. It only makes sense in today’s energy climate to know how one’s driving affects the resources being used.
By JON RUSEL on May 24, 2007 | Reply
here’s an example of the backward force of the air (in pounds) against a corvette at various speeds.
You can easily see that
(mph) 15 30 60 90 120 150
Force 3.60 14.5 58.0 130 232 368
THEREFORE: Always drive DOWNWIND and you will get much better mileage. Do the math.
By 427Galaxie on May 24, 2007 | Reply
Josh–
While most of the information you have posted is correct, EFI engines do not completely shut off fuel when the throttle is closed (foot off the gas). The IAC (idle air control) valve, or sometimes it’s called the IAB (idle air bypass) allows a small amount of air to enter the engine when the throttle is closed. Fuel is also injected to match this small amount of air, which will produce a small amount of power, but it performs an important function: combusting residual lubricant and atmospheric vapors which would otherwise contaminate the combustion chamber and create high emissions and possibly misfires. These vapors would eventually damage the catalyst if they were not burned.
Typically, mixtures in high manifold vacuum conditions (low or negative engine load) are configured to be very lean, but I have yet to see an injector pulse map configured for zero pulse width.
A common trick for modern automatic transmission vehicles to conserve energy while coasting is to disengage the lockup torque converter, similar to (but not the same as) pushing in the clutch or shifting to neutral in a manual transmission car. In any situation, the idle circuit in an EFI equipped vehicle should produce the lowest fuel consumption; if you are traveling at any speed while idling, you should be getting the best mileage possible from your vehicle.
As JWC said, probably the best inexpensive indicator you can get to measure fuel economy is a vacuum gauge. Hook it up to manifold vacuum, and modulate your throttle to maintain the highest possible value as you travel.
By Josh on May 24, 2007 | Reply
427Galaxie:
I’m no car expert. I just like to work on cars. I’ve used a computer program (VAG-COM) to monitor my 01 volkswagen jetta, and when I’m not on the gas the injector duration is zero milliseconds. I thank you for your information because it makes sense and will probably be useful to me in the future. I’m planning on programming a microcontroller to monitor my vehicle MPG real-time after I gather more information. I just wish automakers did this for us.
By Taras on May 24, 2007 | Reply
First of all Gas quality is important than Engine load, Speed, RPM. these things will dictate your MPG. Things like AC, Wind resistance, Up-hill road will dictate your engine load. there is a sweet spot for every gear, try following 18wheeler less wind resistance = better MPG finally buy a device that can help you monitor your engine better I use Scan Gauge II
By Chris on May 24, 2007 | Reply
Thanks falk (#31). I knew there was someone out there that didn’t get a C in HS Physics like I did that could back me up with the formula. So when you double your speed, you get 8 times the wind resistance. Luckily the wind resistance starts at zero, and doesn’t go up very much at first. So as an example, when V goes from 1 to 2 to 4, the cube goes from 1 to 8 to 64.
By Billy Bob on May 24, 2007 | Reply
Great to see you guys are all knowledgable in theoretical nonsense. Go back to making your tacos.
By cory on May 24, 2007 | Reply
Turning off your vehicle at a long stop light is a terrible idea. Starting a vehicle uses more gas then letting it run for 15 minutes on idle, deisel engines are even worse starting up.
By 427Galaxie on May 24, 2007 | Reply
Josh–
Perhaps VW has a system that I know nothing about to reduce or eliminate the problem of lubricant contamination, it wouldn’t be the first time I’ve learned something new. Do you know if you are measuring actual injector pulse width, or just looking at the map coordinates? Some maps will have a base fuel used for idle and start, adjusted by the O2 sensor, with the rest of the map referenced from the idle (as zero).
By Josh on May 24, 2007 | Reply
I don’t think it uses idle as a zero reference. When I am idling, I do see the pulse measurement being above zero. I also was thinking about your post about just watching manifold vacuum and I when I got into my Jetta at lunch I started wondering about how that works if the engine is turbo charged like mine. I’m getting ready to install a boost gauge so if I want good mileage should I want to avoid boost (+) pressure or try to maintain (-) or zero?
By Brian Carr on May 24, 2007 | Reply
Cory - That’s completely incorrect; there’s no way in hell that starting your car wastes the same amount of gas as sitting in idle for 15 minutes.
By 427Galaxie on May 24, 2007 | Reply
Even with a turbo, maximum fuel economy should occur at or near peak manifold vacuum, so avoid boost if you’re looking for highest economy. Boosting is like raising atmospheric pressure… the greater the delta pressure upstream of the intake valve and cylinder pressure, the more filling will occur. The more filling that occurs, the more fuel you will need to keep stoichometric in the combustion space.
Another trick that can be used (and is) to reduce fuel consumption at steady cruise or low throttle angle is to inject an inert or oxygen poor gas into the intake. This displaces available reactive oxygen in the cylinder and reduces the amount of fuel required to maintain stoich, assuming sufficient power is available to maintain cruise. There is a convenient supply available on most modern cars: exhaust. Known as, and often hated on carbureted cars, exhaust gas recirculation (EGR) supplies an amount of exhaust gas into the intake stream. It works fine on closed loop EFI cars, but without good feedback, it’s often a pain to tune and adjust. As a supply of an inert, relatively dry, warm gas, EGR does a couple of good things besides reducing fuel consumption: warming the air/fuel mixture to improve combustion and reduce HC emissions, and reducing combustion temperatures to improve NOx emissions. I have heard of experiments using water steam as a form of EGR, but this requires additional equipment, as well as the possible risk of contaminating the crankcase.
By Zac on May 24, 2007 | Reply
Blah, okay honestly… Im an amature on the road… About a year of driving…. Im 17, and own a 2002 chevy Silverado 2500 HD Crew Cab.. Yea it drinks gas, like a middle 40’s guy who lives in the country.
Yes, its mine….
Anyway.. Gas prices where I live are around 3.25 a gallon.
Here is my stance on this whole gas thing:
The price of gas, or any product sold to the consumer, is based indirectly by the consumer.
In other words, the price of gas is based on YOU! (somewhat…) I take economics, marketing, im in DECA and stuff. so i have to go through business world.
So here you have two options…
Option A!
You learn to accept it. Pay the prices, and eventually wait it out, and hope it gets better.
Option B!
Be frugal about your gas prices. You cant really boycott gas.. As we all need it.. I need gas to get from school to work to home… But be stingy about it. This in effect lowers the gas prices indirectly, and slowly.
My personal option you may ask? Option A.
Here is why.
Face it, there is no point in trying to boycott gas. It er.. It just isn’t going to work.
Even though the gas prices are determend by you the consumer, there isnt really a way your going to be able to change the price of gas because too many people need it. Its way easier for gas to go up than down. I i see a million people buying my gas, then I raise the price. but if 200,000 out of those million ppl stop buying gas, I may lower prices 20 cents and go on with life.
Remember you effect the price of gas in a very indirect, but ultimately direct way.
Okay so enough of that crap here is how i see it.
EVENTUALLY it will even out.
im 17…
still got 80 years, if im going by the 100 scale..
I need gas.
So i learned to accept the fact that gas costs money.
Im not in a position to go buy a prius or however you spell it…
Just pay the price.. no sense complaining about it.. theres nothing you can really do.
Some other things you can do to make that gas seem a littl cheaper?
it costs me 83 and a half dollars to buy a tank of gas.
If I skip morning coffe at caribou, every other day, I save 27 dollars a week.
I if i skip buying food every other day on break at work, I save 25 dollars a week.
thats what 52 dollars?
think of the little things in life you can go without.. I work in a grocery store, and a car repair show.. i see ppl come in with a bag of chips, and a coke, candy, crap we dont need. sometimes you need to put your priorities straight. to me gas is far more worth it than a snickers bar, or a latte in the morning.
Just wait it out, things will get better…
if not then we are screwed lol..
By Kevyn Miller on May 25, 2007 | Reply
A couple of years ago the BBC program Top Gear put tested various economy driving tips using an Audi A8 (diesel V8) using the cars standard fuel consumption computer.
Driving slower did save fuel.
Accelerating slowly did save fuel, however this may have been due to the programming of the auto tranny. According to Audi it is most fuel efficient to change gears at the torque peak as this allows the engine to operate in the rev band where the engine load has the most favourable characteristics for fuel efficiency. Don’t know if this is true for 4-cyclinders but certainly seems to work with my V6 Nissan 300ZX.
The AC and rear window demister both use a lot of fuel.
The most important thing was to read the traffic to avoid having to brake.
By JWC on May 29, 2007 | Reply
@ Mike
“I think the RPM theory being referred to is talking about the gas millage relative to a single vehicle. Ergo, your Civic will use less gas at 1500 RPMs than at 3000 RPMs.”
Again, this statement is incorrect via oversimplification. If the Civic running at 1500 RPM is at wide open throttle because it’s trying to chug up a hill then I assure you it’s using more gasoline than the one going 65 MPH down the interstate at 3000 RPM.
I’ll say it again, RPMs ALONE are not a good indicator of fuel economy.
“I guess you didnt learn much about relativity in physics?”
You certainly didn’t as this conversation has nothing to do with Einstein’s Theory of Relativity. Everything discussed here can be addressed with simple thermodynamics and Newtonian physics. Next question?
By DRIVNMASTR on May 30, 2007 | Reply
LOOK ANYONE THAT CONSIDERS MYTHBUSTERS TO BE THE END ALL OF SCIENTIFIC FACT IS A MOROON IM TALKING TO YOU JESSE WITH A POST LIKE THIS
yeah… the A/C one is totally wrong. I’ve done tests with my vehicle and the difference is dramatic. The A/C gobbles up gas. Windows don’t. If you need more proof see the mythbusters episode where they test that exact theory.
THE MYTHBUSTERS ARE NOTHING BUT SPECIAL EFFECTS ARTIST THATS IT THEY DONT HAVE ANY DEGREE FROM MIT THEY DONT WORK FOR NASA THEY MADE MOVIES THATS IT. PLEASE SEPERATE ENTERTAINMENT FROM FACT.
LOOK JUST BE SMART WHEN YOU DRIVE THESE TIPS DO NOTHING USE YOUR HEAD
AND DRIVING A HUMMER H2 THAT GETS 6 MPG AINT SMART.
WE ARE GOING TO BE PAYING 5-6 DOLLARS A GALLON IN THE NEXT 3 YEARS SO ENJOY IT WHILE GAS IS “CHEAP”
By Pal on Jun 6, 2007 | Reply
The best speed to drive consistently at depends on the car’s gearing and it’s aerodynamics, as well as your driving habits. I drive a Scion xB which is a motorized brick as far as drag is concerned. Once I hit 5th gear wind resistance is my biggest enemy- the faster I drive the more energy needed to counter that resistance.
Putting the manual trans in neutral and coasting when possible, never going over 60 on the highway, and keeping the tires inflated properly. I did just those things, and my mileage over a month went from 31mpg to 36.
There’s a guy who’s blogging his new Beetle TDI and getting in the 50-60mpg range while still going 65mph on the highway with a few changes to the car. Every car varies, find what works for you and when it’s time to get a new car pick one that’s not a gas hog.
By Sean on Jul 16, 2007 | Reply
Re: The below quote.. What a load of bollocks. There’s no way any manafacturer would purposely design peak efficiency at a level beyond the legal speed limits (SUV’s and that 85 mph “peak”) Whoever wrote that forgot rule #1 of fuel conservation: Don’t drink the stuff!
” Most cars reach peak efficiency at around 60 mph, while trucks and SUVs reach theirs around 85 mph. It’s still wise to experiment with your vehicle to find your peak as opposed to guessing or living in ignorance”
By Spad on Nov 29, 2007 | Reply
my jet burns 3300 gallons of gas an hour. I could drive a semi to work and not make a difference on my carbon footprint. Sure makes a difference in my wallet though. Ride a motorcycle, just watch out for drivers in their cages on their cell phones. Especially if they are 16 year old girls. That’ll ruin your savings any day.
By LMF on Dec 3, 2007 | Reply
Why do cars get less mileage at incredibly low speeds than they do at medium speeds? Howstuffworks.com has the answer somewhere (I forgot where), but here’s what I remember:
When the car is stationary, with the engine idling, a car experiences its worst possible fuel economy - it’s not moving, but it’s wasting fuel. Thus you’re getting zero miles per gallon in this state. The fuel burnt when idling goes into: keeping the engine going (specifically, supplying energy for the compression strokes), charging the car battery, powering electrical devices (fuel pump, engine computer, radio, lights, AC fans), as well as the A.C. compressor, power steering hydraulic pump and power brake vacuum pump (which I will henceforth refer to as “accessories”).
Now, let’s say you shift into first gear without using the accelerator and get the car moving slowly, while still at idle speed, through use of the clutch (or by letting an automatic car “creep” on its own). You are now burning the same quantity of fuel as you were before. Some of the fuel is now used to overcome rolling resistance in the tires, some to overcome any slight incline, and most of the power is going to all the accessories and things I already mentioned. Therefore your fuel economy is still very low in this state. (Note that at this speed, air resistance is negligible).
As the car’s speed speed increases, the “overhead” (i.e. power wasted in keeping the accessories powered) remains constant, whilst the energy required to overcome rolling resistance and air resistance increases. This means that at higher speeds, a greater proportion of the car’s energy is being used to do useful work. For a small increase in fuel consumption, the car gets a relatively large increase in speed (at low to medium speeds). Eventually, the speed increases so much that air resistance becomes the predominant force holding the car back, and this is where the efficiency starts to fall again as a large increase in power output will only give a small increase in speed (and hence distance).
From this, I hope you can see why both excessively slow and excessively high speeds are bad for fuel economy. I’ve heard that fuel economy peaks at around 60mph.
I think the best way to get good fuel economy is to have a small light car with a small engine - not only will the car be lighter (i.e. will require less potential energy to go up a hill and hence will use less chemical energy), but you will also have less reciprocating and rotating mass (lighter pistons, crankshaft, gearbox etc.). Small engines consume less fuel in general (especially when idling in traffic) than big engines, even at full throttle. And b.t.w. a toyota aygo (not sure if you have this in America) with a 1 litre petrol engine of 60bhp gets 65 mpg and has a top speed of over 95mph. Think about it, do you really need a car that can do 130 or 150mph, considering how much extra fuel a big engine will use?
P.S. to JWC (#78): He meant things being relative to one another (i.e. “the honda is a small car RELATIVE to the big pickup truck”) not THE official theory of relativity by Albert Einstein
By whammy on Dec 4, 2007 | Reply
LMF(84)–
Your statement about a small light car with a small engine is true, but such a creature would be short lived outside an urban environment in the U.S. Downtown New York? Probably OK. Downtown LA? OK too, as long as you stay off the 101. Anytown, Midamerica? Likely a bad choice.
Where I live, there are lots of heavy (40 ton) vehicles traveling at interstate speeds (75 MPH). Simply put, it would be unsafe to attempt to drive among those vehicles if the contrivance of your choosing was incapable of accelerating and maneuvering among them. Entering a highway and expecting those heavy vehicles to avoid you because you are too slow is an accident waiting to happen. Until highway speeds are reduced by government order (or we license and control vehicles according to capacity like Germany), this will be a reality.
When I buy a car, this is the primary reason I purchase an upgraded engine, not because my ego needs inflation. Excess capacity for acceleration can actually be a safety factor.
By cptn on Mar 26, 2008 | Reply
m4yh3m,
Regarding RPM, that’s a common misconception, but it’s almost complete bullshit. Under ideal conditions, an engine at 3000RPM will use the SAME amount of fuel as an engine at 2000RPM. The main reason higher RPM uses more fuel is due to increased frictional loss (since engines do not operate under ideal conditions). You may be thinking that an engine at 4000rpm will use twice as much fuel as one at 2000rpm. Not true. The engine at 4000RPM will need less fuel per stroke than the 2000RPM engine.
Higher RPM DOES use more fuel, but the effect is not dramatic, especially during high speed highway driving.
What is dramatic is the increasing aerodynamic drag on the vehicle. Think about it. At 60 or 80mph, what is the primary force that the engine has to overcome? Air resistance. The power required to overcome air resistance is a cubic function with respect to velocity. What this means is a car that needs 10 horsepower to cruise at 50mph will need 80 horsepower to cruise at 100mph. Basically a doubling in vehicle speed requires EIGHT times more power.
So don’t look at your tach and think “Oh, I’m only at 2000rpm, I’m doing great!” Look at your speed. Above about 30mph, air resistance becomes the PRIMARY use of the engine’s power. Engine RPM has negligible effect. An engine will always burn the amount of fuel that it needs for a given POWER OUTPUT, not a given engine speed.
Source: mechanical engineer
By Ernest on Apr 17, 2008 | Reply
Tips to Save Gas
Here are simple tips to save gas. These tips will allow you to spend lesser amounts on gas. Ultimately, these tips can also save the environment as well.
Save gas by braking the correct way:
You can easily save at least 10% to 25% gas by braking the correct way. Especially when there is a traffic jam, try to press on the brakes as little as possible. This works because the vehicle consumes the most gas while accelerating than already moving. So by using this simple tip, you can save a considerable amount of gas.
Turning your air condition off:
If possible, try to use your air conditioning as little as possible. Doing so will reduce gas consumption. You can also try to open your windows to increase the airflow within the vehicle.
Reducing the weight in your car:
By reducing the weight in your car, the amount of gas it takes to move the vehicle can be lowered. This is a simple tip to save on gas.
Purchasing a more fuel efficient car:
This is obvious. Purchasing a more fuel efficient car will reduce the amount of gas needed to travel a certain distance. Not exactly a tip to save on gas, but it works.
Car Pooling:
Another obvious one. Carpooling reduces the amount of vehicles on the road, which translates into lesser use of gas and the increase in environment friendliness.
Source:
http://www.tipstosavegas.com/
By EK on Apr 28, 2008 | Reply
Hey guys sorry to tell you all this, you can go out and buy a so called “great economic car” thats “great on gas” but you know what it all depends on how you drive. Me and my friend drove his car which is an old 1980’s boat with a 3.4L V8 and for 100kms we lost 1/16 of the gas tank because we never had to pass anyone or accelerate, of course when we stopped and he had to accel each time it burned a bunch of gas. Why? Because acceleration burns a shitload of gas not coasting. Oh btw the A/C thing, it does burn a tiny bit of gas, but not a lot i don’t know where you people get this stupid idea that having A/C on consumes most of your gas. IT DOESNT, the use of A/C consuming your gas can be (if even barely) be noticed on really long trips.
By EK on Apr 28, 2008 | Reply
Oh by the way we were going 160+ for a whole hour.
By DC on Jun 10, 2008 | Reply
THE MAIN THING THAT I THINK WASTES GAS IS TURNING YO’ CAR ON & OFF & BACK ON AGAIN. THAT SWALLOWS GAS!!!
By Anon on Jul 12, 2008 | Reply
the a’c is worse than the open windows
By country mouse on Jul 13, 2008 | Reply
not so fast Sparky. The general consensus on AC versus open windows is that it depends. You need to measure it for yourself and use your results for your own vehicle and nobody else’s.
In my 120,000 mile old Volkswagen golf I get about 3 miles per gallon more with air-conditioning than I do with the windows open. In my wife’s Chevy S10 pickup (disposed of long ago), it didn’t make a difference. It was a gas pig either way.
The other advantage of air-conditioning is that the car becomes quiet enough you can hear if emergency vehicles are coming and you remain cool enough that you can respond to almost any traffic situation calmly and effectively. In other words, air conditioning helps you be a better driver.
By Anonymous on Oct 25, 2008 | Reply
this is way to long
By nico on Nov 21, 2008 | Reply
fantasti website
By xeen on Mar 7, 2009 | Reply
Depends on the way you drive and what kind of car you drive, and some other factors that the AC is better. I dont use nothing as much as possable, even your vents DRAIN your battery, that make the alternator that charges the battery draw significantly on the engine, so much that if you were to turn you idle air control valve off run the engine and then turn on the headlights and vents the car would stall!! Anydraw on your engine is not good, but using the air in 120degree arizona weather is a good idea.
And fuk mythbuthers haha.
By Matt on Mar 26, 2009 | Reply
As each car is different - if your car has a “instantaneous fuel use” display mode, use that and pay attention to when it is sucking it down.
I drive an auto and have noticed for example that doing 50km/h through local traffic zones uses more fuel than doing 55 through the same areas due to the gear it selects.
In my car, accelerating to 60km/h at a decent rate then sitting at that speed uses less fuel than dragging out the acceleration over a longer time.
Each car is different… you need to try a few things