GMT800 Suburban Towing issues: Gearing or power?

[Martinjmpr]

E85 is gonna suck hard, iirc it's about 10% less energy potential than 87 octane. You're going to get lower power AND lower mpg from it.

Worse mileage, yes, but less power? If the engine is designed to run on higher octane E-85 I would think it should have MORE power, just worse fuel range.

I have run several tanks of E-85 in the truck and in terms of power, I haven't noticed any difference, but that was when we had a lighter trailer. I haven't tried E-85 with our heavier trailer.

WRT mileage, it's not that bad. I actually sat down and calculated the mileage differences between E-85 and E-10 (which is pretty much all they sell around here - finding ethanol free fuel is difficult in Summer and impossible in Winter.) I'm an obsessive data geek (I keep a little notebook in the dash pocket under the radio and record every fuelup on the notebook AND on the Fuelly app on my phone) and the bottom line is that the MPG loss for E-85 is about 5 - 7%. For practical purposes, what that means is that unless I can get E-85 for an $0.75 discount over E-10, it's more cost effective to run E-10. But if, for example, E-85 is $1.00/gallon less than E-85, E-85 is cheaper per-mile, even with the reduced MPG.

 

[rcab87]

On my 2011 Sierra with the 5.3, GM says it makes 315 horsepower and 335 torque on gasoline and 326 horsepower and 348 torque on E85. So according to GM anyway, you make more power on E85. Mileage does indeed suck though.