More torque for my GMC Sierra 4.8?

[bruceb58]

...as shown by his 1 MPG gain from installing lower gears.

I always question people's MPG gains. My mileage can vary a couple MPG tank to tank. That's why you see people claiming 20% mileage gains from using snake oils.

 

[NYBo]

Miracle mileage increasers often "work" because they cause the owner, now attuned to fuel economy, to have a more disciplined right foot, whether he realizes it or not.

 

[SDSeville]

Miracle mileage increasers often "work" because they cause the owner, now attuned to fuel economy, to have a more disciplined right foot, whether he realizes it or not.

That makes sense, and my #s were from one tank (always buy same grade at same station) with less than perfect speedo #s. However, I had a very heavy foot enjoying my newfound power.

 

[SDSeville]

I always question people's MPG gains. My mileage can vary a couple MPG tank to tank.

Very true. Just finished my second tank and it was down 1 mpg from original gearing (-2 from last tank). Oh well, I didn't regear for mileage anyway.

 

[H20Rat]

you also need to consider at what rpm his engine will be operating...
lower rpm absolutely doesn't ALWAYS give better MPG... lugging an engine below it's torque peak can very easily hurt gas mileage as shown by his 1 MPG gain from installing lower gears.

In my car, I get better MPG' s at 60 mph in 5th gear (2600 rpm) vs 6th (2200 rpm), even though the engine can easily handle the load at 6th. That used to be somewhat true in carb'ed vehicles, but EFI makes peak torque far more important. (peak torque for the car is ~3000 rpm)

Non forced induction/non-direct injection gas engines usually need to wind out quite a bit to get near peak torque, I'm guessing the OP's 4.8 is probably around 4500 or maybe even a little higher.