Is Coasting or Engine-Braking More Fuel Efficient?

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Admit it: as a teen, you were coasting to the closest gas station on fumes.

Let’s take a trip down memory lane. You’re a teenager, driving your first car. This is way before there was that amazing BMW in your garage. We’re thinking about when you were lifting couch cushions for spare change. Like many of us, you probably were driving on fumes, with your gas light on, trying to figure out if you were going to make it to your closest gas station. Your A/C is off. Windows are closed (because you’re being aerodynamic and less wind resistance means better gas mileage, obviously). You’re just looking for every trick in the book.

One of those tricks was probably coasting. In your mind, you were probably thinking, “If I don’t put the car in gear, then I won’t be using gas. So, we’re riding in neutral as long as humanly possible.” Did you ever wonder if that actually worked?

In a recent video, Engineering Explained tackled the question, “Is coasting or engine braking more fuel efficient?” Was 16-year-old you a gas-saving genius or an engineering idiot? As far as that query goes, and many of life’s other big questions, host Jason Fenske says in the video, “It depends.”

Engineering Explained Fuel Economy Testing

In the scenario of a sloped road with the destination being at the bottom of the slope, your best bet is actually to keep it in gear and use the engine braking to come to a stop. In the video, he demonstrates this by showing that the MPG gauge reads 99.9 as you utilize engine braking. In this scenario, your engine is running solely off the movement of your wheels and transmission, using zero fuel.

However, engine braking isn’t always the best. If you’re going down a slope that has smaller hills in the path, the constant going up and down just wouldn’t be good with engine braking. You’ll find that you’ll have to engage the accelerator to make it up those smaller hills. If you’re coasting, on the other hand, your natural momentum down the slope will give you enough speed to tackle the other hills, similar to how a roller coaster works.

Look, we’re not engineers, and if you want the full breakdown in better, more scientific terms, definitely check out the full video. Engineering Explained is always good for giving you an interesting fact that you can bring up to all your other car friends. If nothing else, you can just keep reminiscing about all the silly, stupid things you did to save gas, and all those gross things you’d find in the couch cushions.

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