GM 6.0 vs 8.1

Steve_Kibbe

Steve_Kibbe

Well-Known Member
Joined
Oct 26, 2005
Location
Spartanburg, SC
Kicking around the idea of a 2500 suburban for the wife.
We have a 22' pontoon boat we pull to the lake and a 16' flatbed trailer for hauling our 37 hp John Deere around.

Any thoughts as to which motor would better serve our needs.
 
Steve_Kibbe said:
Kicking around the idea of a 2500 suburban for the wife.
We have a 22' pontoon boat we pull to the lake and a 16' flatbed trailer for hauling our 37 hp John Deere around.

Any thoughts as to which motor would better serve our needs.
Click to expand...

I've had both. Currently still do. Drive and tow with the 8.1, the 6.0 is one of our work suburbans now.

The 8.1 is nice in the mtns to keep up with the diesels.

But I'm shopping for a 6.0 suburban with the 6 spd auto.

If you are ok with not running 60-70 on the big hills, and want better mileage on flat ground and not towing, definitely go 6.0.

The 6.0 just lacks some on big hills towing 7500lbs. But I feel the 6 spd would be a huge improvement, and can give up some speed to get better mileage average and especially empty.

Flat land, towing lighter weight, or empty very little difference other than a big difference in fuel mileage, especially around town.

Best I can get with 8.1 in town is 9mpg. Best I can get on hwy empty is 14.

The 6.0 can get 13 around town, and 16ish highway.

I've gotten as little as 3 mpg with both in big hills but the mileage is very similar towing, but the 8.1 gets a little better.

Empty or flat land towing, 6.0 wins.

Want to buy a 2500 avalanche with 8.1?
 
We have 6.0s in all our delivery trucks at work (used penske box trucks) and they are very reliable. We have several at 300,000mi and they have never been babied. People abuse rentals and we have sever that leave the yard grossing 13k daily. We had one spin a crank bearing a week ago but it already had 220k on it. I have 5 more that have never had engine issues.

If you plan to do much towing I would stay away from the 6spd tho. Loaded, they search for gears like crazy. My 2 newest trucks have 6spds and one is on its second and the other is on its third. I will not buy any more with that trans. For regular driving they seem to do fine and help your mileage a bit but like I said, for much towing I'd stick with the 4spd. I've never had a 4spd go out, ever. Maybe they have worked out the kinks with the 6spd, but I won't find out.
 
I had a 2004 6.0 Yukon XL (1500, not 2500), and best mileage I could get on the highway was 16.
 
I have towed with about everything diesel and gas, ford 460, v10 Excursion, Ford 6.2, chevy 454, 6.0, and a 8.1 2500 suburban

As far as gas motors go, the suburban with the 8.1 would walk the dog on anything listed above, the new Ford 6.2 is nice also though
 
I have a 2500 yukon xl with 8.1l and 200k miles. Love the torque and ability to hold speed on the hills. Wouldn't mind a few more mpg's though! I average between 9.5-10 around town empty and 13-14 on the highway loaded up with a couple hundred pounds of luggage and such. Got about 8.5-9 mpg hauling 6k around town. Haven't hauled for any long trips with this one yet so I don't know what towing highway mpg will be, but I expect no worse than my 1500 yukon with 5.3L that got about 9-9.5 mpg and would slow to 50 on big hills.
 
I'd love to take an 8.1 and build a 540 stroker with a nice, torquey cam. I read an article about it a while back and it sounded like fun.

I've got a 6.0 that I swapped some 243 heads on to, did a TBSS intake, 90mm throttle body, 8.1 marine injectors, long tubes, and a custom grind cam. It would make a damn good setup for a tow rig and it's a pretty simple setup that uses a lot of factory parts. You could leave the stock heads on it and still run 87 octane if you really wanted.

However, I also have a Duramax powered 2500HD and my CUCV with the Cummins in it...they both still manage to pull 15ish when towing and 18.5 empty. The 6.0 gasser does 12-13 all the time and it's 10.5:1, so it gets 93 octane.
 
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