Should You Coast in Gear or in Neutral to Save the Most Fuel?

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If we were looking to save a little bit of fuel on our next Jeep adventure, should we engine-brake or coast in neutral?

We love our Wranglers. But if we were to sit down and have an honest conversation about the Wrangler, we’d honestly say that the fuel economy is nothing worth bragging about. Yes, that’s not why you buy a Wrangler, but it’s still true. What if you were looking to save some fuel, however?

2018 Jeep Wrangler Lineup

If you’re cruising down a hill, should you leave your Jeep in gear–automatic or manual–or should you shift it in neutral to be the most fuel efficient? Our friends at Engineering Explained created a video to discuss this very scenario.

When you coast in gear with your foot off the accelerator, the car turns off the fuel injection system. The engine is still turning, but that’s because it’s still in gear and gravity and inertia are keeping the wheels turning, which keeps the engine turning. You are not using any fuel at all in this situation.

Putting your Jeep in neutral is fuel efficient, obviously, but not as fuel efficient engine braking. In order for the engine to stay turned on with the vehicle in neutral, some fuel is required to keep the revs up enough to prevent stalling. You’re basically idling, except you are moving instead of sitting still.

ALSO SEE: What the Forum Has to Say About Efficiency

 

The only scenario that isn’t addressed, and also isn’t particularly safe, is putting a manual transmission car into neutral and then completely turning off the ignition. You’d get all the benefits of inertia, even going up a hill, but you wouldn’t use any fuel at all. Restarting the engine is as simple as popping it back into gear and putting the ignition into the run position.

As always, your mileage may vary, but many of us are probably already engine braking as we approach traffic lights and stop signs, so we’re already saving a little bit of fuel here and there and not really even realizing it. More fuel in the tank when we get to the off-road park means more fuel to burn, which is always a good thing!

Chad Kirchner is a regular contributor to Corvette Forum and Ford Truck Enthusiasts, among other auto sites.

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