[QUOTE="94CumminsRed, post: 29301528, member: 996403] I've got a 2.5" leveling block in the front and a 5" block in the rear, with 35's. Also aftermarket bumpers, so I won't have the air dam.[/QUOTE]
Not the best recipe for efficient use of fuel. If good mileage is a priority you have two options. Get rid of the lift, big tires and big bumpers or buy a rice burner. If you want to just improve what you are now getting it is the same old mantra. Slow down, ease off of stops and ease into stops. With proper driving habits you can get decent mileage, but I doubt it will be as high as 18mpg combined. I'm happy with the 15 I achieve. Changing speedo gears is a math problem. If you are showing 60 when you are actually doing 70 you need to install a gear that has fewer teeth. In that instance if your present gear has 30 teeth you would need one with 26. 60 divided by 70 (.857) times the number of teeth on your gear. (.857 X 30 = 25.7).