Looking at getting a 2500 Suburban with the 8.1 and getting rid of my duramax truck. I like the idea of being able to haul more people and keep everything inside as I don't use the box for much of anything anymore and tow a trailer when hauling anything. This is only used for towing and not a daily driver. Ive been getting around 10-11 mpg with my diesel and paying .50 a gallong more than gas so I figured the 8.1 cant be much worse. Any opinions on power and mileage along with the vehicle in general would be appreciated..
I have a 2005 2500HD with the 8.1 Allison, 3.73 gears. I have run 285/75/16 and 265/75/16 tires on it.
Unloaded, I got 13.8-14.5 mpg @ 75-65 mpg respectivley on the interstate with the 265's, I get about 13.2-14 mpg on the interstate with the 285's. There was a slight reduction in fuel economy unloaded with the larger tires. It will probably be very similar with the 'Burb ... I would think you'd lose a little less power through the 4 or 6L85E tranny than the Allison, but the 'Burb weighs more .... so its probably a wash as far as unloaded highway driving. In town you'll probably get 9-10 mpg.
Towing my 16' enclosed snowmobile trailer that weighed at most 4,000-lb with two sleds and gear this truck didn't even break a sweat. It'd pull that at 75 mph down the interstate in OD. I would get between 8-9 mpg towing this trailer in virtually all weather conditions down the highway. Interestingly enough, I got exactly the same mileage with my 2000 5.3L with the
same trailer and it wasn't even funny how much better the 8.1 pulled it. I also get exactly the same mileage pulling my dad's 26' Charmac, which is right aroun 6,000-lb with 3 sleds and gear. Its more difficult to pull that trailer in OD @ 75 mph down the interstate ... it will hunt for 4th and 5th on the flats, 3rd up grades.....all of this is with the 285 tires mind you....If you have 4.10 gears and 245 tires, you will be better set up than I will and it probably won't hunt as much with a trailer that big.
In another week I'll tell you how well this setup does with a really big trailer, as I'm going to pick the new one I just ordered up .... so I'l be making the trip from Nampa ID to Vernal UT with this same truck, but with a 31' encosed trailer that will probably clock in at somewhere around 5,500-lb empty. I'm fully expecting to get between 7.5-8.5 mpg towing this trailer mixed 65/75 mph driving.
I will let you know how it goes.
Bottom line: No, the 8.1L is not a mileage queen, but its quiet and it
always starts when its cold. Its cheaper to buy, own, refuel and insure.
Are you gonna win any races with it? No .... but, its a setup that works very well for what it was intended for overall.
