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I got in a disagreement with a friend of mine over manual transmission FE.
My wife's Xterra is manual and i was just curious about hypermiling in it and trying FAS.
I was telling my buddy about it and the conversation evolved into FE at a given gear and rpm.

I understand that your mpg will be better if you can get to 5th gear in as little time is possible. He was saying that if you were going uphill and were in 5th you would use more fuel since its harder to maintain that gear. I guess pressing down on the accelerator more than if you were in say 3rd. My thought here would be his rpms would be higher/ using more fuel.

I'm no expert with man. transmission and have only driven them a few times. So what do you guys think?

Someone can correct me if I'm wrong but this is how I think of it. I think it just has to do with simply how engine effiency works. It really has nothing to do with the hill either. In a basic sense, it's less efficient to produce the same amount of power at a higher rpm. That is exactly what happens when you swap between 4th and 5th going up hills.

If you can make the exact amount of power needed to get up the hill in 5th at a constant speed it will be better than making the exact same amount of power in 4th to get up the hill because the rpms/power ratio is lower.

Think of this extreme example: would you rather drive 70 MPH in 4th gear down the highway or 5th gear? A quick glance at a scanguage will tell you that higher gears are best, if possible, for going up hills though. I've tested this many times. Even if I'm not exactly correct in my reasoning, it seems it is ALWAYS better to give the car more gas pedal in 5th up a hill than drop to 4th and let the rpms increase.

Hi Ryan:

___He is sort of close … Pulling the trailer and gear with the Ranger as an example. Sometimes I do get higher FE in fourth then fifth depending on speed and slope. I am constantly shifting between the two to match a peak of at least 25 to 30 mpg’s while towing if that helps? With just the Ranger itself, 5th and DWL like mad for 40 + in a steady state cruise of sorts ;)

___Good Luck

___Wayne