As I have stated before, this is the first diesel I have owned. It seems to be getting around 17 mpg. Most of the others at work who own diesels are getting 20 or better, What can I do to improve mine.

Have you done a compression test to make sure it's in good condition? Have you done a tune up on the injection system? Maintenance is the first step.

17mpg out of an IDI? I'd be thanking my lucky stars.

Averaging around 17 MPG from the 6.9 is pretty good. There's really not a lot of stuff that can be done to them to get big numbers of MPG.

You can change how you drive, oil type/viscosity, air filter, headers/turbo, etc.. but 17 is pretty good.

I had an '86 with 305K on it and it averaged about 17.5 MPG and 1 qt. of oil every 200 miles. At 65 MPH it was topped out and on the governor. The only thing it would pass was a gas station.
Joe