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Hipermiling on a automatic transmision

I’m really interested on hypermiling. I have a 2009 automatic Hyunday Elantra, and I’d like to know if it would damage the transmission if I do the following:

While driving, say I’m going down hill, where I need to slow down gradually, Id I take the stick from D to N, to put the engine on idle, and then at the bottom of the hill, switch the stick back to D and keep driving. All this witout stopping, but just slowing down. Would this damage the transmission?

Thanks for any help!

This is asked over and over and over, including at least twice in the last week. Please see the link marked “Search” above!

Well first it is illegal in many states to put your car in neutral. It is a safety issue. In addition, you may actually decrease your mileage. Most modern cars today will turn off all fuel to the engine as long as the engine is turning over at or above idle speed. If you put it in neutral, it will start using fuel (decreasing mileage) as long as it is in neutral.

At this point you are looking at a number of factors determining what combination of techniques are going to give you the best mileage. Your driving habits, the specific car, the wind, rain, temperature, hills, traffic, traffic lights etc. all need to be considered at the same time as they interact.

If you really want to know, you will need to do some test with you as driver in your car at the usual temperature and humidity, traffic, wind, load in car etc.

You are talking about something that is best considered an art. There are just too many variables to really know the answer.

Search this forum for “coasting in neutral” and you will find many discussions on this subject.

It won’t damage the transmission, but it will ever so slightly reduce your gas mileage, instead of increasing it.

I’ve said it in these pages before and I’ll now say it again. A lot of these hypermiling techniques, when applied to everyday driving, are boneheaded and dangerous. Leaving the car in gear while driving downhill will help you slow down while using NO gas (see Joseph E Meehan’s post above).


Simple rules to save gas:
1-keep the car in perfect tune
2-drive smoothly, calmly, unagressively
3-obey the speed limit
4-most of all, reduce your driving, eliminate unneeded trips, combine others, carpool, etc.
You’ll save 10X the gas with these…

Well put!!!

This topic has been done to death. But no it won’t damage the transmission, but you won’t actually increase your fuel mileage either. Modern engines stop firing the fuel injectors when you are coasting. By putting the transmission in neutral the engine will idle, which means it’s using fuel.


No, it will not damage the transmission providing you engage the transmission at the bottom of the hill. If you try to guess when to engage the transmission when you start uphill, you could be causing damage.