The Stovebolt Site Forums The Shop Area Engine Shop Gas Mileage and Drivng Style's Debate

My brother and I are currently in a heated debate over 2 topics of driving styles.

The 1st topic is about what gear to drive in and if it is detrimental to the transmission and engine. Currently in the truck is a fuel injected motor, with a 5 speed. I like to shift to a higher gear while driving, for example in a 25mph zone I will drive in 4th gear at a low rpm where he likes to drive in 3rd gear at a higher rpm. He states that having the engine run so low (approx 1500rpm) is not good for the engine and transmission where as driving at closer to 3000rpm is better. The major thought is I get better gas mileage and he is just putting a bit more wear and tear on the engine out by running it at a higher rpm.

Our 2nd topic of ongoing discussion is when driving up a hill is it more gas efficient to have the pedal pushed to the floor(again running at a lower rpm) in a lower gear or to downshift to a higher gear and have the rpm’s higher.

The way it was explained to me years ago was you can either run high rev's and have more engine wear or low rev’s and have carbon build up. I try to keep my 283 and 350 at the 2000 RPM range.

Going uphill the higher rev’s give you higher HP and better GPM and less engine knock.

I'm sure others will have varing positions.

Low RPM's is good, up to a point. You don't want to be lugging the engine too much. You also shouldn't be over revving it with real high RPM's. You should be able to listen to it and tell when it's running comfortably. If it's winding too tight, shift up a gear--if it's pulling too hard, shift down one. A 5 speed gives you plenty of options.

Vacuum is a good indicator of fuel economy, when you floor it up a hill in high gear, you have no vacuum so there for no fuel economy. Install a vacuum gauge on the truck and try both driving styles again, I would bet that neither is idea, but a combination of both is the best.

Waisted rpm is waisted fuel, yet real low rpm does the same thing since you have the throttle open so much.

Joe

This would be a great question to phone in and ask on Car Talk, hilarity will ensue.

In my personal opinion, I think that this is a silly question.

Not because of the question itself, but because there are to many variables to consider to even come anywhere close to a scientific answer.

Everything from size of engine, to how many miles are on it, to how it is tuned, rear axle ratio, gear ratios in the transmission, air in the tires, weight of the vehicle, and on and on and on it goes.

I think you could take two completely identical vehicles and still come up with mixed results. Then it has to do with how the driver reacts, when they shift, what rpms, and on and on again we go.

Just my thoughts. I don't think it can be answered in a reasonable fashion.

So maybe your both right, or maybe your both wrong!

Jeff

it depends on what you are driving, if you are driving a small block chevy in a truck that you just use as a daily driver, not hauling stuff in it. This whole argument is pointless, it is obvious you aren't really concerned with fuel economy in the first place. Now it may be fun and cool and all, but fuel economy isn't even in the equation.