Why Using Neutral May Not Help Save on Fuel
July 12, 2012
You see it there between Park and Drive, that ambiguous "N" staring back at you. You may think “When am I ever going to use it? I drive an automatic!”
Well, you're not alone - many drivers often think the same thing. But contrary to popular belief, "N" does not stand for "Never use" in an automatic transmission vehicle! There are times when it's appropriate to use Neutral - and times when it isn't.
In a manual vehicle, Neutral is used to buffer the engine when switching gears in order to disengage the engine from the transmission. In an automatic, there are fewer uses for Neutral. One of the biggest misconceptions about Neutral is you can save on fuel by using Neutral to coast to a stop while driving.
We've all been there - you’re almost out of gas, you see the light blinking from the corner of your eye, and you panic. “How am I going to make it 5 more kilometres to my nearest Petro-Canada gas station? Eureka ! I’ll just pop it into Neutral and coast all the way!” Good idea? Not so much. Here's why.
First off, you always want to keep alert and be in control of your vehicle while you’re driving. If you are in Neutral and need to suddenly put your foot on the accelerator – maybe to avoid something – you won't have time to put the vehicle back into Drive and it will be too late. This is the same reason why you need to keep both hands on the wheel. In an emergency, you need to have full control over your car – that goes for braking, turning and accelerating.
Secondly, we want to debunk the myth that putting your car in Neutral saves gas. We here at PumpTalk are always looking for ways to save on fuel, but coasting in Neutral is not one of them. It's true that when you place your car in Neutral, the engine is idling and consuming a minimal amount of fuel. BUT, as you approach the stop light or destination you are coasting to, the engine beings to wind down further, and it then goes into survival mode - it begins to work harder to keep the vehicle from stalling. This happens at about 1,000 RPM and under.
At this point, you begin to use more gas than if you are in gear and just have your foot off the accelerator. So in the end, your efforts to save on fuel have been countered by your engine struggling not to stall. You can find a more detailed explanation in this Popular Mechanics article.
Thirdly, you may also be causing stress or damage to your engine if you happen to put your vehicle back into gear while coasting. Shifting gears, even in an automatic, is done at specific speeds. If your vehicle is coasting in Neutral at 60km/hour and you put it back into Drive, your engine may not be in the right gear because it has not gone through its natural progression of shifting from low gears to high. This may not blow your engine, but can cause additional engine stress.
So when can you expect to use Neutral in an automatic vehicle? The most common uses of Neutral are when your vehicle has broken down or you have run out of gas. You may need to push your car to your destination to have it serviced or filled up. In this case, popping it into Neutral allows you to push the car. If you need to start your vehicle and are not able to put the vehicle into Park for some reason, you can put it into Neutral and start the vehicle. Neutral and Park are the only settings that allow you to start your car. And of course, you use Neutral when you are going through a car wash!
So when you see that low fuel light flashing and you think: “Neutral Time!”, think again. You may not make it to your destination if you do!
Did this explanation help you rethink how you use neutral in your automatic vehicle?
- Julie S.
I think you should edit the paragraph that debunks fuel consumtion in neutral for clarity; it is misleading.
When in neutral, the same amount of fuel is being consumed whether you are rolling or stopped. The engine is disconnected from the final drive and it is left to spin only the torque converter and transmission input shaft.
When the vehicle is in gear, the situation is different. If you are DECELERATING with your foot off the gas pedal, the wheels are turning the transmission, and the trasmission is turning the engine, the opposite of acceleration. This means very little fuel is required to sustain RPM. As the vehicle comes to a stop (in gear still) the wheels stop rotating, but the engine is still turning. This is where the torque converter comes into play, it acts as a fluid coupling between the spinning engine crankshaft and fixed transmission input shaft. This fluid coupling imparts a resistive force on to the crank shaft, making the engine require slightly more fuel than if it were in neutral.
To summarize: the most fuel efficient way to drive an automatic is to leave it IN GEAR when decelerating, and to put it IN NEUTRAL when at a stop.
Posted by: Jon | July 13, 2012 at 02:29 PM
Thanks for the suggestion!
- The PumpTalk Team
Posted by: Petro-Canada | July 17, 2012 at 08:22 AM