Mr. Truck,

I met a fellow horse hauler/camper last week and had an interesting conversation about mileage.

I have a 2005 Chevy 2500HD 4x4 with a 6.0L engine. He has a 2001 2500HD 4x4 with the 8.1L engine.

Very similar trucks and trailers but my engine is smaller.

I get 8-9 MPG whether I am hauling or not and he gets 15 hauling and 18 not hauling.

1) Is my mileage way too low for my truck?

2) Is it really possible that having a larger engine cna get better gas mileage? His logic was that the bigger engine does not work as hard. My problem with that is that my truck gets virtually the same MPG whether I pull or not.

thanks

You don't say in your post... Are the two rear axle ratios the same too? His 8.1 had the Allison transmission or a manual. The 8.1L had two axle options 4.10 and 3.73, Your truck didn't have the Allison or the 3.73 axle option. The 4.10 axle alone will reduce your cruising MPG.

Whooo, I don't have any ideas about the axle ratios. I'll try to find out what mine is but I don't know what his was.

We both have automatics.

So it sounds like the mileage difference has more to do with axles than engines.

How can I determine what my axle ratio is?

I'm pretty sure your 6.0 truck had a 4.10 axle.
But you can double check by looking up the RPO code in the glove box. There are three character codeson a sticker that list the options as installed by the factory. You have to do the search by model/year as GM recycles codes.

quote:

Originally posted by BigDaddyRoach:


So it sounds like the mileage difference has more to do with axles than engines.

It takes a given amount of hp or energy to move a certain mass. Cruising is mostly wind and tire resistance. The bigger engine will be able to produce hp at a lower rpm than a smaller engine so it's more effective at burning fuel for motion.

This basic law of physics keeps me from believing the old story about the 100 mile/gallon carb design that the oil companies bought and buried. A gallon of gasoline is not going to power 6000 pounds of vehicle along 100 miles of level road. (maybe in outer space, but not a regular road)

I think my RPO for the gears are:
GMC GT5 G80

Which I think means 4.10 and limited slip differential.

Maybe a bigger engine would help but i don't think and 8.1 as opposed to my 6.0 could account for double the mileage (8 for me vs 15 for him).

I guess I am stuck with this fuel hog.

thanks

By the way, where in NC are you located? I'm in Welcome which is betweeen Winston-Salem and Lexington.

We're close by each other... I'm in Stokesdale. between WS and Greensboro.

The transmissions will help reduce the cruising engine RPM too. The Allsion has 5 gears, I believe yours the 4L80-E has 4 gears.

So there are two items that have a huge effect on MPG. Plus, like fishermen and their fish, the hauler's MPG grows with every telling