When to use overdrive?

volvo
gasoline
240
transmissions

#1

When climbing a hill, if the engine RPM is sufficent, is it better to select overdrive (5th gear) or leave it in fourth? Does going to 5th use more gas? I don’t think it exessively wears the engine, since the engine is not “lugged”. Thanks


#2

Presumably this is a manual transmission?

There is no clear “better” as it depends on what you are trying to accomplish.

In general, you get the best fuel economy in the highest gear available that won’t result in the engine lugging (bogging/lurching).

You will have more torque in a lower gear, however. In general, I’d say pick the highest gear that will allow you to maintain the speed that you want/need to maintain. Sometimes this will mean that you may be downshifting and upshifting while driving up a hill since the grade can be changing on longer climbs.


#3

Yes, it’s a manual transmission. My wife and I are still not agreeing on this. She likes the security of having some margin of power whereas I don’t think it’s necessary. But thanks for giving us your opinion.

Steve


#4

Over the years of doing transmission work. I’ve found that using 5th gear under heavy loads tens to wear out the rear bearing in the transmission. In 4th gear, the power is going thru the transmission straight. In 5th gear, it is using the counter gears and puts a load on all bearings in the transmission, It can also create a problem down the road with the transmission popping out of 5th gear under any loads. 5th should be used only for fuel economy without putting a load on it.