Quote:
Originally Posted by Eddie25
so was going to ask which is more efficient but did some homework and found that it is more FE to coast in gear rather than neutral in a manual car. I will be changing my driving style accordingly. I can understand if it is a slight downhill the engine braking might cause you to get on the gas a bit sooner. but I live in hilly terrain so a steep downhill is 90% of the time followed by an incline so I need to get on the gas sooner anyway.
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Eddie, I do not believe there is a one-size-fits-all answer to your question. In my diesel Golf with a manual transmission and a turbo I frequently coast in neutral with the engine on
unless I need to slow down. In the VW coasting in gear results in fuel cutoff, using no fuel, proven by the ScanGuage and by ear with the windows down. In my diesel Jeep Grand Cherokee automatic the fuel does not shut off when engine braking and the computer controlled automatic transmission really does not like coasting in neutral. Gasoline or "Petrol" engines have much better engine braking than diesels and will lose momentum quicker than a diesel. The diesel has lower pumping losses than a gas engine and my car injects only 0.13 gph in neutral netting 350-400+ mpg while coasting in neutral. I drive for mpg and for car longevity so I choose to leave the engine on coasting to save wear and tear on my car. Also, I have a 7 mile downhill where I have to shift into 3rd to keep from speeding and in summer I will even put the A/C on high to put some additional drag on the engine without a mpg penalty. So I think it all depends on the situation.