When we were running the GM 3500HD (LVT) we had to feather the fuel nozzle. However when we had the Chevy 4500 the two OEM tanks would handle the flow on the low setting. The Chevy 4500 also had a in-bed 98 gal tank and the fuel nozzle would work on the top setting. And now with the Freightliner we have twin 80 gal tanks and they will handle the highest setting. Jay if you get a Freightliner you will never go back. The ride alone is like night and day over a steel suspension thats on all the pick-ups. The best selling point is get the little lady into the Air ride seat, and take her for a ride. The first time Delaine ever sat in a Air ride seat was in Elkhart, Ind. at Chariot Vans upfitters, she looked at me and said I want this Truck. I called the dealership who was having it upfitted and bought the Truck on the phone. So when we went to a heavier and larger 5th wheel she started looking for a Freightliner, we couldn't afford a new Freigthliner (cost $120,000+). So she found a pre-owned 2006 Freighliner with 50,000 miles for less than a Ford F-450 and will out last the F-450 without a doubt. Good Luck, there are pre-owned HDT's and MDT's out there and you will have a Truck you don't have to ever worry about weight issues. And high mileage on the HDT's and MDT's are in the range of 750,000 miles, anything less and you will have a Truck that will out last most RVer's life. GBY...