the 8100 is one bad mutha. too bad it's thirstier than a biker in a harley bar on dollar-draw night.
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No doubt. I have a 3/4-ton Suburban with the 8.1L and 4.10 rear end, which is good for towing 12K lbs as a tag. Most trucks support that much weight only as a gooseneck/5th wheel.

I am averaging, long-term, 11.6 mpg without the trailer, in mixed driving, and 7.8 mpg with the trailer, which is a TPD enclosed triple-axle 24', weighs probably 7500lbs, and has extra height. But yeah, the towing performance is amazing. Prior to this trailer I was towing a 40' aluminum gooseneck with 2 cars, towing with a Chevy Duramax diesel, and let me say that I think that this 8.1L tows every bit as well as that diesel did. Of course, the fuel mileage isn't as good.

Unfortunately to get the 8.1L now, you have to buy used.