rpm/ fuel eco

[Graham Ritter]

so i was just wondering, i was driving along the other day and i was going up a hill with the over drive ON (city driving), and i thought about how i had to give it more gas to get up the hill at the same speed, then a day or two later, i went up the same hill, only this time i had my o/d OFF, and it didnt have to shift down and i didnt have to give it more gas to get up, so what i was wondering, if my RPM was at 27,30, and i was going 50mph, would i be getting better mileage than when i was at lower rpm and had to hit the gas a little more... sorry if im not making any sence, i know the max torque hits around 2,500 so thats where i figure i should try to keep the rpm, am i correct?

 

[Michael Cacioppo]

In a lower gear ( O/D off) your engine has a more favorable mechanical advantage. Just because the engine is at a lower RPM, doesn't necessarily mean that it is operating more efficiently. Engine torque also varies with RPM, I believe there may be more available engine torque at 2700 RPM than at 2500 RPM. I'd run with the O/D off in the city. IMHO