I'm hoping for some opinions on fuel mileage and performance from members who have experienced the 6.0L Vortec in a late model dually. Soon, I hope to purchase a new GMC dually, double cab, 4x4, with SLT trim. Heavy! After several months of on-line research, I still cannot determine which engine will be most practical for me. I keep vehicles for a long time, and will be replacing my 1988 GMC K3500 SRW with the 454/TH400 that was purchased new and is still in excellent condition at 64,000 miles. I use this truck primarily to haul a 3,000 lb. slide-in camper during the summer months, with a few seven mile work commute trips thrown in. Rarely driven during the winter months. So the big question - will the higher revving 6.0L be annoying to live with in such a heavy truck - empty and loaded? I live in the Pacific NW, so lots of mountain passes and hilly terrain. I want to be able to keep up with traffic though, which the 454 does well with. A larger, 4,000 lb camper will be purchased in the near future. A trailer will not be considered. I want the added stability of the dually platform, which should reduce some of the white-knuckled driving situations in the current truck. The expensive Duramax just seems economically impractical for the relatively low annual use the new truck will get. The 454 with 4:10 gears and 3 sp. auto gets 10 MPG highway empty/8 MPG with camper. It would be nice to improve on those numbers after spending $50,000+ on a modern truck. Any thoughts? Should I just save up for the Duramax? Thanks!