Fuel Economy Tip – Coasting

Today’s tip probably won’t help you save much on gas (unless it gets you to start doing a better job of anticipating driving conditions), but it will help to keep you safe while you’re coasting down the road.

When you coast, keep the car IN GEAR, not in neutral.

This tip goes along with a previous post, which was about coasting to a stop as opposed to continuing to accelerate only to slam on your brakes at the last minute. In this post, I pointed out that you would get much greater gas mileage by simply easing off the gas and coasting to red lights, stop signs, etc.

What I failed to mention though was the fact that you should keep your car in gear as you coast.  Many drivers, especially those with manual transmissions, tend to put the car in neutral as it coast towards the red light or stop sign, which is rather unsafe to do.

The reason putting the car in neutral is unsafe is now you don’t have the ability to “hit the gas” if for some reason you had to make an evasive move.  For example, as you’re coasting, something comes out in front of your car (another vehicle, an animal, a person, it doesn’t matter) and you need to get over into the other lane quickly.  If your car is in neutral, you’re going to slam on the gas expecting to quickly accelerate, only you’re not going to go any faster.

Additionally, you’re vehicle will have much better handling if the car is in gear.

So, go ahead and keep the car in gear, only switching to neutral once the car is at a complete stop – coasting in neutral isn’t worth the risk.

Comments

  1. I don’t agree with coasting as being unsafe for manual drivers as if you are an experienced manual driver, hitting the gas to speed up is done at the same time you throw your car into a SPECIFIC gear that will cause you to dart out much faster than a gear you have to get out of first.

  2. Brian Carr says

    Or, you can just be in gear and then downshift to accelerate quickly.

  3. Not exactly related to this post, but I’m glad to see that your tips take into consideration safety of the driver. Some tips cycling through the media and the internet can be unsafe to the vehicle and the drive. I read a tip from a newspaper that it’s better to drive your car until the fuel tank is empty, since it’s less weight to carry. However, the fuel that gets used below a quarter tank or so can contain dust and other solid particles that can cause damage to your fuel injector and engine. It’s always important to keep in mind that saving a few cents per gallon doesn’t mean anything if you have to perform costly maintenance every few months.

  4. Brian Carr says

    Thanks for the feedback. I agree with you – which was why I was quasi reluctant to post the daytime running lights tip. Although, I’m not convinced that they actually make the road safer.

  5. I have a manual transmission car and I normally practice coasting. However I put the gear into neutral while coasting because it gives better speed than in gear. Many times I see the red light and put my car into neutral gear and as I approach the light, it turns from RED to GREEN. The speed of my car is at a level that I can directly move into the third gear to drive further. Is this practice harmful to my car’s transmission or any other car part?

  6. Thanks for the comment. I also drive a manual transmission car and there have been plenty of times that I will see a red light up ahead and pop the car into neutral so I can simply coast up to the light. Again, this is probably one of those do as I say, not as I do things because this isn’t the safest practice in the world and I wouldn’t actually recommend doing it.

    In terms of whether or not it hurts your car to coast for an extended period of time and then put the car back in gear, while I’m not an automechanic or an automotive engineer, it doesn’t seem to me that this is something that would hurt your car, unles you either go into too low of a gear (causing your engine to hit extreme RPMs) or too high of a gear (causing your engine to bog down and ping).

    Hope this helps.

  7. I don’t agree with the safety aspect much, however the real point to coasting in gear is that in a modern engined electronically injected car, when the wheels are turning the engine (i.e. in coasting in gear) no fuel is needed or used. Hence coasting in gear, although it slows you quicker than coasting out of gear, will save you more fuel as you are using more than when the engine is idling with you out of gear.

    It will also help your engine keep cooler when coasting in gear as the water pump will be driven faster.

  8. ratedsar says

    Just being in gear doesn’t mean that you’ll be ready to move when you hit the gas, unless you compression brake like crazy your rpm will be low and probably away from it’s power range… aka if you’re under 15mph you’ll still be in 2nd or 3rd (because first is hard to shift down to) but you’d be able to move much more quickly in first.

    Stay in gear though because most ECUs shut off fuel until they’re under 1000 rpm or gas is being added as Chris said.

    Downshifting also significantly saves the brakes.

  9. i think coasting is ok if you are an experienced driver my friend drives 30 miles a day to work 15 miles each way , on the way back it is down hill (slight decline) all the way and this is on the highway he accelerates to 60mph and then goes into neutral for 14miles untill his turning comes up

  10. the injectors cut off when the car is decelerating in gear anyway, so it seems you’d get better mileage in gear anyway IMO

  11. what about in my automatic .. when taking an exit with no traffic I can put my car in neutral and my rpms drop from 2 .. 2 1/2 to less then 1… is that not saving me gas… safty aside…

  12. I am from Mauritius Island – Indian Ocean. I’ve got a Manual 5 Speed Mazda Familia Break – Year 2001, 1500CC, Fuel Injected Engine of Course. My Question is that: For this Car Model, do somebody know if their injectors fully cut off (I am stressing on the FULLY CUT OFF – NO FUEL AT ALL) when coasting with the fifth gear on a lengthy down-inclined road with the Engines RPM around 2400 and Speed of around 87KM/H, foot off accelerator of course..Thank U very Much…

  13. To the best of my knowledge/reasoning, the injectors would completely cut off. Otherwise, it would be like spraying fuel out of the front of the car to it slow down! However, in response to Chris Key’s post, what I would say is that if the wheels are turning the engine, then the engine is slowing down the car, which would then require fuel later on in order to speed it back up again. I’d appreciate if someone would correct me as necessary on the following:
    – In a carburettor (throttled) engine, freewheeling WILL save fuel, since the fuel-air ratio is fixed by the carburettor. By closing the throttle, the engine is forced to suck in the mixture against a reduced pressure, but the fuel is still combusted and the power developed is wasted on the said suction.
    – In any fuel injection engine, free wheeling would save LESS fuel since fuel consumption is approximately a product of power selection and RPM and since full power means maximum fuel input at each opportunity (and no power means no fuel input, as above) and higher RPM means more ‘opportunities.’
    However, since the engine is being ‘driven by the car,’ it will slow the car down, hence will waste energy, unless the engine is being turned over at tick over RPM, in which case coasting in or out of gear *wouldn’t make any difference.* I can’t help but feel that simply switching the engine off in such a circumstance would be the only way to save fuel, although I understand that jump starting the engine when need can cause some damage.
    (NB I’ve never driven a fuel injection car – since there is no throttling, they should possibly have less engine braking; is this the case??)
    – Manual transmission: the above applies as red.
    – Automatic transmission: depends on the design, since the torque converter might waste a tonne of energy if neutral isn’t well put together.
    – Besides requiring more of the brakes, coasting has little effect on the vehicle. Any torque applied to the wheels brings them closer to skidding, therefore leaves less grip available for cornering, while engine braking in a non-all wheel drive vehicle places additional torque on some wheel and means that the non-driven wheels will generate sub-maximal braking force.
    As I said, all feedback gratefully received: it might just help settle an argument in the family!

  14. If you are in gear, and going down a hill with your foot off the accelerator in a fuel injection car then the engine will use no fuel at all.
    If the incline is steep enough you will maintain or even gain speed, if not you will lose speed.
    The engine doesn’t use energy to slow you down, its the compression of the engine that is slowing the car down, you don’t need fuel for that. However in a fuel injected car the ECU will try to not let the engine drop below idle speed, so if your rpm drops below say 1000 it will start using fuel to maintain the engine at that speed.

  15. Anders Rosnes says

    My observations. 1.6 litre gas engine
    Cruising at 70-80 km/h on flat road: 0.56 litres/10 km @ 2000 rpm

    Then look at this situation:
    Slight downhill (just enought to keep car coasting in neutral at 70 km/h)

    Neutral: 0.1-0.2 litres/10km
    5-gear: 0.3 litres/10km
    Neutral, but adding gas to keep engine at 2000 rpm: 0.3 litres/10km

    Point is: At 80 km/h, it ‘cost’ 0.2 litres/10km to keep the engine revving without being connected to the wheels.

    If I were to let the car coast with 5-gear and foot off the pedal in this situation, the speed would go down to maybe 40-50 km/h and people would start getting annoyed around me 🙂

    That is why coasting in neutral pays off sometimes.

  16. I disagree with some of the contentions here. Safety must always be considered first, so only coast out of gear when you are not in traffic.

    I drive a 2006 Toyota Avalon with an MPG monitor. I’ve systematically studied the effect of coasting/not coasting, and coasting in or out of gear and will report the following based on the same route and over full tanks of gas:

    1. Driving without coasting: 19.5 mpg city/hwy
    2. Driving with coasting in gear: 23.0 mpg city/hwy
    3. Driving with coasting in neutral: 26.0 mpg city/hwy.

    The mpg values were confirmed by refueling and checking the gas mileage.

    Recall from physics class about conservation of energy? If you coast in gear you will slow your car down at the expense of kinetic energy. For example, where I exit the highway I have a long ramp with a gradual grade. The posted speed limit on the ramp is 45 mph. When I get into the deceleration lane and shift into neutral I can usually coast up to the top of the ramp while still going about 25 mph. This does cause folks to group up behind me, but it is not serious. If I coast in gear, I won’t even make it 1/3 the way up the ramp before I have to hit the accelerator – this is all caused by the engine braking the vehicle.

    The question I have relates to the wear-and-tear on the transacxle of shifiting in and out of neutral. Any thoughts?

    Happy coasting!

    Tom

  17. chris busch says

    It’s all bull. Coasting is much safer and more fuel efficient than in gear driving, FOR EXPERIENCED DRIVERS NOT IN A RUSH.
    Learning to coast is easy, safer and more fuel-efficient.
    Using the accelerator for accident avoidance is unsafe. Your brain and your brakes are what will save you from disaster.
    Learning how to engage neutral while driving down the road in an auto transmission is what will save you from overshooting in an icy emergency stop.
    To engage neutral while moving forward in any acceleration or deceleration state is as simple as pushing forward on the shift stick.
    It’s designed that way for safety!
    Use this transmission option for coasting and emergency icy stops.
    Coasting in neutral will save brake pads when coming to a stop, will save fuel, will require less effort for a stop.
    Best not to use coasting in a vehicle that is not idling properly. Don’t leave the vehicle in neutral when at a complete stop on an incline with an automatic transmission (problems with regularity in driving habits in different situations)
    Never coast through an intersection while making a turn (problems with regularity in driving habits).
    Never use coasting when you mind is not on your driving.
    YOU MUST BE PAYING ABSOLUTE ATTENTION TO YOUR DRIVING WHEN USING THE COASTING METHOD and at all times for that matter.
    The best time to coast is down hills. Only skilled coasters should expand to other situations.
    Carmakers don’t design auto shut off and turn on engines with electric peripherals because this will save fuel. A hybrid is the closest alternative to using the coasting method.
    Buy a hybrid that uses battery power for the main power source and saves the on board engine for battery charging. I believe it’s called a series hybrid.
    THE COASTING METHOD SHOULD ONLY BE USED BY EXPERIENCED DRIVERS
    Why is coasting safer? Because you must pay better attention to your driving, you must drive slower and you must leave more space between you and the car in front of you.
    Don’t coast if you are in a rush, if you are a tailgater, if you’re a cell phone junky, if your attention is likely to be taken by passengers, etc.
    The safest way to coast is by leaving your vehicle in drive and timing the lights so you never have to come to a complete stop at a stop light.
    The best way to save fuel is to never use the accelerator to go beyond the speed limit and ultimately driving lower than the speed limit.

  18. chris busch says

    I forgot to mention one thing about coasting.
    Never coast down steep inclines where you are likely to over speed before the bottom of the hill.
    Always leave your transmission in drive for that situation. You must use the engine resistance in parallel with your brakes to keep you from over speeding.
    AsKa big rig driver if he/she would ever coast down a steep incline in neutral. NEVER.
    Problems with getting the vehicle back into gear when over speeding, and problems with over revving should you choose the wrong gear.
    NEVER USE COASTING METHOD ON THE HIGHWAY.

Trackbacks

  1. […] No, it does not cut the supply in neutral – the car must be in gear. Engines running in neutral use fuel to keep a constant tick over – engines left in gear turn themselves over without the need for fuel. All explained here: Daily Fuel Economy Tip

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