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When spotting a red light or similar, I often release the gas pedal, gear down and let the engine decelerate instead of pressing the brake pedal. I was taught that this was more energy efficient for some reason, but I never really understood why. Is thIs true?

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Might be worth reading… –  Cornelius Jun 14 '14 at 11:38
I've removed two theoretical answers, including the accepted one. Please remember that we don't allow answers based on mere theoretical models - you have to link to evidence. –  Sklivvz Jun 16 '14 at 22:53
The only efficiency claim is one that I've anecdotally tested with the trip computer on the car. Downshifting to higher revs, and coasting, causes the instant fuel consumption to report 0.0l/h. But braking only reports 1.1l/h (l/h is used over l/100km when not throttling). So hardly a massive difference in economy, and personally not worth the extra wear on the gearbox. But also sounds very, very cool if you have a large capacity engine or a nice exhaust. –  Mark Henderson Jun 17 '14 at 3:37
I think there was even a mythbuster episode where they tested all of this quite precisely. Depending on the conditions I would say that I personally save 10-15% with this style, as this is about the only major difference in me and my wifes driving style. –  PlasmaHH Jun 18 '14 at 10:03
I think the problem is that this question is a bit too vague - the type of vehicle being driven and a whole lot of difficult to track variables come into play. Some examples: A hybrid/electric car may benefit more from the use of the brake, as this causes the battery to be charged. An older carburetor style car as previously stated may offer no efficiency savings. Then their is the energy cost of replacing brake pads as well as the potential wear and tear on the engine. Finally you may need to consider safety - you probably have more and better control of your deceleration with the brake. –  Chris Noldus Feb 10 at 3:04

protected by Community Jul 4 '14 at 1:31

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