I wish I knew for certain that today’s tip actually does help you get better gas mileage, but even if it doesn’t, you’ll have the nicest looking car in the neighborhood.
Regularly wash and wax your vehicle.
If this idea actually works, I wish I could take credit for it (if it turns out to be a scam, you didn’t get the idea from me). While searching other gas saving sites, I came across a tip that claims if you wash and wax your car, you can improve your gas mileage by up to 7%, which based on today’s prices would be about $.27 per gallon.
Not too shabby.
The basic idea behind it is, after washing and waxing your car, the surface of the vehicle is much more likely to be nice and smooth, therefore, it should be more aerodynamic than when you have lots of bug guts smeared all over.
It looks like a sound theory, but I don’t know if simply cleaning your car will increase your fuel economy that drastically. However, it’s worth a shot because at the very least, your car’s going to look nice.
Especially if you’re NOT kicking sweet rims.
{ 58 comments… read them below or add one }
7%? No way. Maybe if you have an elephant smeared on your trunk, but that’s it. Plus, the cost of wash/wax materials is going to offset that cost and make it not worth it (assuming the looks don’t matter).
That’s the most retarded thing I’ve ever heard.
It’s technically reducing the surface friction… I’d doubt that 7% is anywhere near the real figure, unless you had 400 pounds of dirt caked up under and on your vehicle. None the less, friction is friction and reducing any way possible helps in some way.
This is fairly absurd. Yes, surface friction figures into a car’s drag, but the overall shape has a far heavier influence. Perhaps this tip should have been called something to the effect of “buy a car with a low coefficient of drag.”
Heck, if you’re washing the car that often, you’ll spend all the money you’re “saving” on wax, soap and heating the water.
I don’t want to be pedantic (ok, I do), but improving your gas mileage IN NO WAY REDUCES THE COST OF THE GAS! IT reduces how much you burn to drive a particular distance at a particular speed with a particular load, yada yada yada. Assuming this is even true (which I doubt), a 7% improvement on a 35 mpg car gains you not quite 2.5 mpg. Or barely half a mile per gallon in your 8 mpg beguzzlehemoth.
If you REALLY want to improve your fuel economy, buy a fraking Vespa.
A classmate of mine once worked at the local FedEx terminal washing trucks. Every night. I mentioned to him that it seemed like a waste of money just to have clean white trucks. His response was that FedEx had studied the problem, and determined that washing the trucks every night saved them millions of dollars a year in fuel costs (company-wide, of course). Of course, FedEx has many, many trucks, and they all drive many, many miles a year, so while washing your car regularly might save you some money, it’s the economies of scale that really make it pay off.
7% is for airliners, which go 550 mph and have no tire/road resistance. Cars would be more like .1%.
….until you decide to open a window.
Pfft. My Honda has probably 6 pounds of bird shit on it and still gets way over the EPA highway mileage. And I usually am going 75-80 mph.
Yep, it’s pretty unlikely for any automobile. However, weekly washing and biweekly waxing do more than reduce drag.
By washing you’re removing dust and dirt that the vehicle may suck in into the air filter, which will reduce gas mileage. Keeping your car cleaner keeps your air filter cleaner as well. This also in turn means your engine is generally taking in slightly cleaner air than if the car were dirty, keeping it cooler and more efficienct.
When you wax you decrease the friction of your cars’ surface, decreasing the amount of dust, dirt, and polen that will stick to your car, while only a miniscule amount, if you go, say 2 months without waxing or washing, the figures could definitely become noticeable.
“nice and smooth” isn’t always good.
Ask a golf ball designer.
More info, aero drag accounts for only about 2.4% of total energy loss. [link]
Make that 2.6% of total energy.
So cutting your aero drag by 50% (unlikely) should lead to an average 1.3% fuel mileage increase.
This cannot be true. I concede that when you accelerate, your car spends most of the energy on moving itself, but once you are at a steady speed, the rolling resistance is ridiculously low. You can check my own calculations (for F1 cars on a totally different topic) here. Using the same Excel sheet (corrected by the members of the thread I gave you), I find that, at 100 kmh, for every hp spent on overcoming rolling resistance you spend 10 hp (13 actually) overcoming drag.
On the Excel worksheet, I used 99 to 100 kmh (to avoid divisions by zero for kinetic energy), 2 square meters frontal area, 0.3 CV. Look at rolling resistance and drag figures. Please, take in account these are “power to the wheels” data, as the thread explains.
BTW, you can easily check if I am right, assuming that the equations for drag are correct (as CFD designers do…
) and measure your car rolling resistance. Simply, take it to a low speed (to minimize drag losses), let’s say 40 kmh (or 30 mph, for example) and let the car coast to a stop. Measure the distance it traveled. Your coefficient of rolling resistance is simply half the speed in kmh (20 kmh = 6 m/s) squared (36 m/s) and divided by distance. It should be around 0.01. This are the watts you spend by every kilogram your car weights and the meters it travels.
this is true, i have been waxing and washing my car since i was first able to drive and i believe that it is totally accurate. after a good cleaning and waxing you car feel less wind resistance and the car slices through the air better. exspecially on windy days. so quit being so fricking lazy and couch potatoed and get your fricking self out and take care of your car.
Wow! Glad people are reading this blog!!! Happy Birthday Brian!!!
Washing your car also helps it last longer by removing the crap that traps moisture (dirt and bug guts) against your car promoting rust. Less friction = better mpg. Lisa, “That’s the most retarded thing I’ve ever heard.” — you need to get an edumacation.
and here’s a book to prove it!
pops up
Ithink I once read that ups washed its planes for the same reason
Good God. Who thought that the most mundane idea I’ve ever posted would get this most attention.
Keep in mind, I too am skeptical of the 7% increase in gas mileage, I just posted what the other article stated.
Also, to the person that stated that improving gas mileage does not improve the cost of gas – yes, you are right, you’re going to spend money on gas, and probably close to the same amount, but if you can get better fuel economy, you’re going to fill up less often, so that’s where the savings comes in.
Just out of curiosity, how did all of you find this blog?
Forget waxing the car, I’m gonna smear KY Jelly all over the car and get 10% better mileage!
The guy who mentioned golf balls has the right idea. If the surface is perfectly smooth, air isn’t slowed at all and you end up with a larger vacuum behind the car, aka DRAG. That’s why golf balls are dimpled, to slow the surface air down so less vacuum is created, allowing the golf ball to go faster and further. Lisa said it best.
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A dimpled golf ball travels further than a smooth one with the same stroke. So I was wondering why race cars aren’t dimpled. Would they go faster? Would dimpled passenger cars get better mileage? I will take a nail and hammer and go try it right now. Wish me luck.
The golf ball example is not a valid comparison. The dimples decrease the speed required for the flow to transition from laminar to turbulent. In this transition range the pressure drag drops dramatically at first. However as you continue to increase speed the drag will eventually increase with increasing speed.
That’s what I like to see.
i was led here by fark.com
I’m not familiar with Fark.com, although I’ve heard of it. What sort of site is it?
Ok, the KY Jelly comment was totally inappropriate.
Fark.com = news and misc. things… a collection of posted links, photoshops, audio edits, etc.
Fark.com? It’s fark. :+P
Hah! That’s ridiculous. But I am glad that people are thinking about gas mileage.
I have a Honda Insight that I haven’t washed in the 6 months. I’ll do a test to see if it works. The fuel consumption gauge will help test out the theory (if I actually wash it today).
On the other hand, increasing the speed from 59-60 mph reduces fuel consumption by 2.65% (2 mpg – I usually get 75 mpg on the highway at 60 mph.)
-John
invisiblegold.com/about/tourdesol
Note: The numbers are from a program called “PowerCalc”. It seems to match the results I get driving.
YAY FARK
It is true actually. People are misusing the government fuel consumption website. That 2.6% is removing an additional 2.6% of the 12% that goes to the wheels. Aerodynamic drag causes a 15 to 20% loss of the energy that was delivered to the wheels.
The golf ball analogy is also way way off. Golf balls travel upwards of 100 mph at times when hit. The reason golf balls are dimpled is because a sphere is an awful shape, aerodynamically. There is no vacuum, there is profile drag, or where the air separates from the surface, leaving stagnent air. The dimples create vortices along the surface, causing the boundary layer to trip to turbulent.
A car, on the other hand, is shaped more for aerodynamic purposes, and has much much less profile drag (though it still has some). I think people are taking this way out of context to. What time period are we comparing? A car that hasn’t been washed for a year vs one every other week? In that case, the actual savings might be closer to 10-15% comparatively. If you wash your car once a week and do the bi-weekly waxing, it will be significantly more efficient than a car that washes once a month or longer.
The advertising machine will love the people who read this. He said “up to 7%” and we all know that means anything between 0 and 7.
So, its most likely true because 1% is between 0 and 7.
approximately 7% is what I have heard for turboprop and jet aircraft, even though it entirely depends on the shape and surface area of the leading edges of the aircraft. Some aircraft have more surface area on the leading edges than others in the same size class and make up for it with bigger engines or slower stall speeds so you cant actually give an exact number tho. However 7% approximate doesn’t sound ridiculous for an aircraft. The approximate wind resistance/fuel economy numbers for washing an aircraft and having sunk rivets (which is another aspect that is commonly talked about in terms of fuel economy) still differ greatly tho from plane to plane…
Uhh…. Aerodynamic boundary layer is nearly the same for smooth waxed paint and bird shit covered paint.
Only coating your car in sandpaper or something to make it totally rough would actually help more, because it will help the flow field stay attached longer and cut down on skin friction drag that way…
Then again skin friction drag is orders of magnitude lower than pressure drag caused by cross sectional area.
Using this logic, stiking my hand out of the window should reduce my fuel efficiency by one half.
http://www.cruel.com
no way i own a vanagon wash it why it’s like a flat box going down the road
Most of the savings will occur during highway travel when a well waxed, clean car will get better mileage. Any type of race car is clean to the point of shaving the edges of decals for extra areodynamics. All those little bumps and bird droppings and rough surfaces on the hood, windshield and roof do slow the airflow down. A cleaned car usually also includes getting crap out of the trunk which is dead weight as far as gas mileage is concerned. Wax on the paint, RainX on the windshield.
Wow. Cool blog.
My head is spinning.
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I just washed my car and I now am getting over 800 mpg. Guess it really does work!
Contratulations. I hope your clever wit takes you as far in life as your 800 mpg will.
Washing cars, checking tire pressure, etc is all good- while you are at it- drop the ski rack – that right there will save you 5 MPG-Easily-
People – you’re missing the BEHAVIORAL element here. Someone who is devoted enough to wash their vehicle weekly is someone who clearly values their automobile a great deal.
As such, they will be less prone to aggressive acceleration, high speeds, and erratic driving that lead to greater fuel consumption. Basically, if they love their car enough to wash it all the farking time, they’re gonna baby it on the roads.
It’s psychological. The people that report 7% are the same ones that lovingly ease their car in and out of traffic, then wash/wax every Sunday.
Interesting point. I sent an email to UPS last night because I had heard one of the reasons they wash and wax their trucks so frequently is because it helped to increase gas mileage.
I call shenanigans.
Golf balls have dimples on purpose to rough up the air right over the surface – to get BETTER aerodynamic properties.
If the dirt on the vehicle weighs alot – then you might see a benefit – but you are not losing mileage to little bumps.
Anyone with enough K-Y jelly to smear on a car needs serious farking help.
Still seems highly unlikely. Give the guys at Mythbusters a call. I’d like to see them try it our on TV!