2500HD 8.1 3:73 need mileage info asap

catpower · September 29, 2001

I am looking at a 2500HD with an 8.1 and 3:73 rear end. I drive 35000 miles per year. What kind of mileage are people getting? 80% hwy 20% city? 4x4 ext cab short box

VegasDude · September 29, 2001

I have the 8.1 and allison. Once you get 4000 miles on it you will get almost 14 on the road with no towing. You will 10+ towing. That is what I am getting now. I have just turned 5000 miles on mine. When I go to synthetic oil I am sure it will improve a little. Oh, I also have the 3:73 locker rear end.

RIPMF · September 30, 2001

Hey there I have a 2001 2500 HD 8.1 gettin around 12mpg right now but I have a heavy foot.Just put durablend in does it really help om the mpg.

Garmat · September 30, 2001

catpower,

I have the 3.73 rear and I replaced the 245s that came on the truck with 265s. I haven't had the recalibration done, but I get around 9-10 mpg. Most of my driving has been city. I've gotten as good as 12.9 but that was driving painfully slow (60-65 mph). The best I've seen anyone claim was around 14.5 mpg. Anytime I get worried about my mileage, I just give her a little romp and that puts a smile right back on my face.

RIPMF · September 30, 2001

hehe I like it when I give my bbc a romp it leaves about 100' of black lines and alot of smoke almost makes you forget its a truck

Timberline · September 30, 2001

If it looks like a big block, sounds like a big block, runs like a big block then it's probably a big block.

Lots of power and allways thirsty.;)

Steve Cornell · October 1, 2001

I have that combo, 8.1\allison\3.73 CC 4x4 2500HD, I get anywhere from 11-14 empty (depends on your speed and how heavy your foot is)

I average 7 mpg towing my 36' car hauler (22,300 lbs gross) the truck has plenty of power and the allison is great while towing.

Mad Dog · October 18, 2001

Iv'e got a 2001 2500HD 8.1L allison with 3.73, I'm HEAVY on the throttle and I got 10.6 MPG last tank. But, I've onlyn got 2400 mi on this thing

jeb · October 18, 2001

Reading these posts assures me I did the right thing. I got rid of a 99 3/4 ton 4x4 454 burb to get my 01 2500HD with the Duramax/Allison. I'm averaging about 17 all around with a high of 19.5 and a non-towing low of 15. Plus I have more power at my disposal that the 454 had. A win-win in my book.