I have a 2005 Mazda 6, AT, 4 speed... I was wondering how much harm does it do to the transmission if you were to put the car into neutral just as you go down a hill then put it back into drive once the hill levels out? Of course this saves gas and allows you to increas speed. I used to drive an 80 something automatic and this allowed me to save an insane amount of gas. I could get 32mpg easly and I live in WV with turn after turn and steep hills. That old car didn't matter to me sense I had a back up and well really I couldn't wait till it died so I could get it out of the way. We have 4-5 cars laying around at any given time. That car was at the end of its life when we got it and that was back in 2000 and it's still running good. We take care of our cars! Right now my parents are using it while they work on thire regular car. So anyway, I have a new car with low millage and expensive parts!!! But of course its MPG on the back roads here sucks. It does great on the highway. It has taken me a while to learn to work the pedal so it won't shift every other second. It can be touchy at times... But anyway, I've given it one test and felt how smothly it can switch from neutral back to drive. And I got 33mpg on the back roads! When I normaly get 22mpg. I'm not about to take this into practice with this new car without some good advice!