I recently bought a 2007 GMC Classic crew cab long bed with the LBZ engine and a 6 speed Allison. It got 22mpg on the 800 mile trip home at 68mph. I tow a 15,000 5th wheel and it gets 10.5 to 12.2 mpg depending on the conditions. I usually tow about 60 mph as that is near the maximum rpm torque rating for the LBZ engine. You can set the cruise and the tow-haul and it keeps the speed up going up the hills. The engine has 50 more HP than my 2002 Duramax and a lot more torque. I am a happy camper with the LBZ engine package and the 6 speed Allison.
Vroadracer
