Ok guys, don't beat me up here. I'm a current F-350 PSD owner. I'm not a Ford nut though, I just like trucks. I'm considering coming back over the the GM world. I went and drove a 2500 HD Duramax today, LOVED IT!!! So did the wife, which, as you all know, actually makes the decisions. My question is this, I was actually considering going back to a gasser, the 8100. I know this is a diesel site, but was wondering if anyone here had any actual stats on gas mileage of the 8100, both empty and pulling. I have a 10K 5th wheel I pull around, and to it's defense, the PSD pulls like a dream, I have the 6 spd hand shaker, and I can set my cruise and forget it. It takes a monster hill to take me out of 6th gear. Anyway, the dealer told me that the 8100 would get about 8-10 mpg not pulling, which I found hard to believe. My company has a 3500 van with the 8100, and it seems to get as good or better mileage than the ones with the 6000, but pulls like a mule uphills.

Don't tell any of the Ford guys I said this, but the GMC/Chevy just looks waaayyyyyy better than a Ford ever thought about looking.

Any advice would be appreciated.

Oh yeah, what about mileage from you Duramax guys. I'm looking at a 2500, CC, SB, 4X4. What mileage are you getting from this truck both pulling and empty.

Thanks, look forward to hearing from you.

I just traded my 8100 gmc 2500 on a 3500 diesel . Empty on the highway 11 to 14 mpg in town mybe 10mpg Pulling a 25 foot 5th wheel 9500lbs. 6 to 8 mpg at 70 - 75 mph. 45 - 50 up hills

Owned a '01 8.1 until I traded for a Dmax with Allison. Same tranny as the 8.1 had. On a good day at 70 mph pretty steady got about 14. In town and some road time about 11. In town (like Vegas) 7 or 8 mpg. Towed Nissan on Dolly across country several times and got 12 to 13 on the road. Downshifted pretty frequently on grades but pretty quick getting off the dime. Nice quiet running vehicle without any problems with engine. Dmax LLY is 18 to 19 on the road and 16 in combined driving 15 or so in town. Virtually no downshift on grades. Not as quiet as 8.1 Both are pretty decent vehicles. Fuel door on 8.1 will wear out sooner than on the Dmax.

2001 8.1 i had got a fairly constant 10-11mpg, none of this is highway miles though. When i towed, i only towed about 6000lbs. Now i have an LLY, on the same daily routine i get anywhere from 14.5-16mpg. the 8.1 got about 10 towing and the duramax gets about 14. I personally think the 8.1 was faster stock than the duramax when unloaded. Neither feels at all taxed when under a load, but the duramax seems to tow easier. Both were allison equipped trucks. the 8.1 was a regular cab long bed 4X4 with 4.10 gears and the duramax is a 2005 extended cab shortbed 4X4 with 3.73 gears.

Like aka said,

I get 18-19 mpg on the highway, cruise set at 75. My last tank was mostly city driving and my average mpg was 15.7. I have a heavy foot. I filled up today and it did cost me $140.00 plus a bottle of Stanydyne. When are the truckers going to strike? And drive down the price of fuel?

Thanks a great deal for the info guys. It looks like I need to stay with the diesel.

XR-Freak, I agree, I don't see how truckers are surviving. I wish they would all just pull over for one day. My neighbor is a driver, I talked to him today, he said he spent $1800 on fuel THIS WEEK!!! Ouch. He said the pull over for a day would be great, but you can't get all the truckers to pull together and do it. The price of diesel just ticks me off. Especially since it's cheaper to refine than gas!!! The only reason it cost so much, is because they know they can get it.

Thanks once again.

i had a 03 3500 DRW 2wd crew cab. it got 13 empty and 11 loaded 5k-10k. the 8100 seems top be speed sensitive to gas mileage. over 77mph it got terrible mileage. id say well into the single digits.maybe 7

current duramax. it got 15 on the first few tanks. 17.5 on the next few. then 19.9 for a while. last 2 tanks im gettin 21.i only have 7,500 miles on it.and loaded i been getting high 14's. very very happy with the empty gas mileage.and just satisfied with the loaded mileage

If you are pulling I would get the diesel. The 8.1 isn't a slouch but a diesel probably would suit your needs better and you already own one. Don't think you would be happy goin back to the gasser world!

ok, the 8100 gasser, 02 Avalnche 2500 model, i was getting 8-10 mpg city and 11-13 highway. i got about 6 towing 10k trailer.

now with the 04.5 DMAX LLY, i get about 14-16 city and 17-19 highway. I do tend to drive fast and when on the highway have been known to carry 90 mph + for long stretches. Now towing the 10k trailer, I get about 14mpg.

That is the reason I went with the DMAX over the gasser. Once I had a taste for diesel, it was had to turn back to gas. It doesn't make sense especially with the rising gas prices. i know prices of diesel has gone up too, but i believe diesel will plain out as the truckers will shut down their trucks causing mahem across the country. this is my $0.02 worth.

Thanks again guys. I think you have convinced me. My current other brand diesel is my second. You are correct in saying, nothing towes like a diesel. The only reason I was considering a gasser was that I didn't tow but maybe once or at most, twice a month going camping. If the gasser was not too bad, I thought I'd save the extra $6k on the purchase, and a few cents at the pump. It sounded like a good idea on the outset, but after further research, not so good.

Someone once told me, when you're towing, what would you rather have, a motor designed for pulling loads, or a gasser. I love my diesels. I may very well be joining the ranks of the DMAX crowd soon, if so, I'll be seeing you guys around here more.

Just to fill you in, the 6 speed allison auto is coming, you might want to wait till this time next year if you can. idk what anyone would think of that idea.

yeah the 6 speed. mpg's are surely to be up. plus i heard that it was to have more hp coming out. i will have to see how everything unfolds before i go for another new one.

8.1L = 11 mpgs empty ave.
8.1L = 7.5 MPGS TOWING ==8000LBS
6.6 = 16 MPGS EMPTY ave.
6.6=12 mpgs towing=8000lbs
these are my numbers . i had a 8.1 for 3 years
my lly i had for 6 mos. 6000mi.

My old 2001 3500 got 8 hwy, 8 towing the bobcat and trailer, 8 hauling the 9.5 foot camper, 8 around town, 8 at 60, 8 at 80. let's just say it got 8.

mikegolfmc, thanks for your service and protection to our country !!, but I would like to know what kind of diesel is in our tanks today ?

Textron AGT 1500 gas turbine connected to an allison transmission putting out 1500 horsepower and capable of burning diesel, jp4,jp5,jp8 kerosene and regular gas.:ro)

A buddy of mine just picked up a 2002 GMC2500HD with the 8100. His is an extended cab long bed 4WD.
What is the best way to beat him in a race with my 04.5 LLY that is bone stock? Probably don't want stop light to stoplight, so do I take him on the freeway flat or up an 8% grade towing 6000 Lbs?

towsaboat.... IIRC the 8100 is rated at like 350 hp and 450 torque.... someone chime in for specific numbers on HP.... but your D/A is rated at 605 torque.... I would think you'd take him. Beware, though the 8100 is a very impressive towing machine.

My friend has a stock 8100 02, crew 4x4. It beats both of mine in the 1/4. about 1/2 a truck length on the LB7 and 1 1/2 on the LLY. (mine are stock)

Quote from XR- Freak "I filled up today and it did cost me $140.00 plus a bottle of Stanydyne. When are the truckers going to strike? And drive down the price of fuel?"<!-- / message --><!-- sig -->

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I suppose when the rest of you are willing to pay our bills. :exactly: :muahaha:

It depends on the year for the 8.1. In the beginning they were rated at 340hp and 455lb-ft. Then for 2003 they were downrated to 330hp and 450lb-ft and they have remained that to this day. This is in the HD trucks though, in the avalanche and the suburban, they use the 4L80E(maybe 4L85E) 4 speed auto instead of the allison/ZF and have always been rated at 320hp and 450lb-ft(not perfectly sure if that is the correct torque or not but i think it is).

yeah the 6 speed. mpg's are surely to be up. plus i heard that it was to have more hp coming out. i will have to see how everything unfolds before i go for another new one. I think the reason for the 6 speed Auto might be possible lower first/second... gears to compete with Dodge and Ford - both are faster off the line especially with a load....

For the same strength the tranny has to grow in size to make room for more parts (and more to break) or the parts have to shrink if the size stays the same. I am happy with my 5 speed as it is.

hmmm, interesting. I may need to look into it further.

Didn't someone mention that is was supposed to be the over drive? Lower R's at higher speeds?

i have considered a gear venders over drive to allow me to split gears and give me a taller 5th.

our current allisons are suposed to have a 6 speed. the whole tranny is set up for it.