The fuel mileage on my 03 has been steadily dropping for about the past year. A trip that the truck could nail 22 mpg's hand calculated by just setting the cruise at 65 now and keeping it pointed between the ditches will barely pull 18 mpg now. Nothing has changed in the truck's set-up since I installed the new turbo almost 3 years ago. I run synthetics in the engine, trans, t-case and axles. Run the tires at near max pressures, and am **** about tire rotations and filter changes. Still plenty of power and nothing really to report concerning hard starts and whatnot. No smell of fuel in the oil or quirky sounds/driving to indicate a possible injector problem, and no codes.

Thus far, the truck has 94,000 miles on the clock and is still on the original lift pump (waiting for it to actually die before upgrading), stock CP3 and injectors. The valves have never been adjusted. New ball-joints and alignment a few months ago.

I'm thinking about adjusting the valves, even though it's pretty early considering Cummins' 130,000 recommendation for the early CR engines, as I've heard of people picking up a few lost MPG's by doing it. Figured it won't hurt anyway.

Any other ideas/thoughts?

 

Try cleaning you MAP and IAT Sensors.

 

Thanks. Actually I tried that about 6-months ago (the MAP and IAT sensors are one and the same on the 03's). Figured it would be looking pretty bad, especially with the exhaust brake as I've heard those can really foul them up. It really didn't look to bad at all, and the cleaning didn't seem to make a diff. I'm wondering if just replacing it would be better? Any idea what one of those critters cost?

 

I'd go ahead and adjust the valves, wouldn't hurt. I did mine at around 90k had two exhaust that were a little tight.