1 The air flow to be Increase will help a good bit and no restriction on the exhaust also. What Is the best oil to use to reduce friction can help some. Keep the tires pump up tight will help also. The way you drive has a big factor so a lead foot Is no good. Now what have I missed on how to Improve fuel mileage. I think this subject Is Inportant with the price of fuel. So jump in with your commets and lets see what we can come up with. Never know. Now I know a clean truck always runs better or Is that a myth? :{