I recently bought a 2003 Chevy 2500 4x4 Crew Cab Duramax. It only has 83,000 miles on it. I have put about 1,000 miles on it since I bought it. Everything is stock with exception of, I replaced the oem air filter with a K&N filter and it has been reprogrammed.

It was programmed with a Hypertech Programmer III to the second setting. My fuel mileage is not that great. Out of this 1,000 miles which was mostly interstate driving, some in town, I got approximately 15 mpg. When I bought the truck, the programmer came with the truck. My question is: Will I get better mpg if I reprogram the Hypertech to the oem setting, or, the setting of #1 rather than the second setting. Also, I know it has a third setting. Which would be better, or is it a matter of trial and error to find the best mpg. I don't want to spend a lot of money on other modificatons such as expensive intakes and exhausts, etc. I am a newby to diesels, but I do love the truck. I will do very little towing with the truck. Heavist thing that I may haul will be a double axle medium duty trailer with a riding lawn mower on it, or the same trailer with furniture and other items when I move my daughter out of college. Did not really buy it to tow. Just loved the looks of the 2500 and have wanted a duramax for a long time and I ran up on this deal. Or, is the mpg the best that I will ever get and I will just have to live with it. Any advice will be appreciated.

I would throw a turbo back exhuast on it so you can take the cat off, that would prob. be the cheapest way to increase your fuel mileage the most and you should pick up some throttle response.

first thing take the hypertech off and put an edge, ppe, or quadzilla on, then like ynotracing said need to let engine breath so exhust without cat will help and intake.
(dont like hypertech because friend had one and did nothing to help milage or HP) Good luck