Your right duffman im not goin to college im goin to uti to be a diesel mechanic!!!! thanks for the sarcasum!!

 

The tires are a big part of the problem. They have a lot more rolling resistance and the inertia is a double whammy on rotating assemblies. Buy as you say, regearing will help reduce how hard the engine works and help improve mileage.

 

If you had the coin for the lift/tire/wheel combo you should be able to afford the gas. Research your financial needs and what the truck is going to cost you. Think realistically and put the truck back to stock if need be. Keep the combo aside and install when you make the bigger bucks.

 

Rolling resistance I will give you, and certainly when you are talking about cruising mileage. But I don't totally agree on inertia of the tires and wheels.

He went up 20% in tire radius. That means it would take 20% more torque to get the truck moving from a stop the way it used to. For a 7,000 lb. truck, that's like putting 1400 lbs in the bed.

Adding 50 or 75 lbs. per tire is going to have an effect on stop-and-go mileage, but I think it would be slight, compared to that.