Dont shy away from 8 cylinders because of mileage. For normal commuting, especially highway driving, some full size trucks are pretty good on gas. Ive owned GMC Sierras 4WD with fuel management 5.3s since 2004 or 2008. I forget which one had the first FMS. Highway speeds 65-70, get 19-20 mpg or more and thats driving terrain in upstate NY, Vermont, and Massachusetts all with plenty of hills. Use cruise control to save on fuel. My normal highway speed is 74-75 a little over speed limit. I usually get 18-20 mph. My overall mileage including with city driving, running around town, highway, and of course towing is 17.3 mph. It tows like a dream and at 6000 lbs has no problems stopping. No swaying (important to use proper drop so trailer is level and not leaning towards back like you see so often. Ive owned GMCs but a buddy has the new Dodge full size and he says he gets good mileage also. So ask around. Dont just depend on window sticker. Ive gotten better highway mileage on every Sierra SLT 4WD Ive owned then whats posted on the sticker. But when not towing, using your cruise control really helps. On level roads Ill use cruise while towing also and I rarely use Tow Mode.