Just last week, my cruise control won't engage at all. The light will come on the instrument panel but neither set or resume/accell will get it to engage. I thought maybe fuse but I can't find the fuse for the cruise control. I also wanted to know if there was anything I could do to increase fuel mileage. I know that there may be a chip or something that I can try. I have a 2003 Dodge Ram 1500 with a 316.

I have a 2003 Dodge Ram 1500 with a 316.
No you don't. I think you're meaning to say "318", but Dodge stopped making them at the end of 2001.

Your cruise control shouldn't be messing up like that. This truck is so new. Something must either be messed up in the servo or one of the vacuum lines is screwed up. Inspect the lines for damage/leaks, and failing that, check the servo for anything wrong. I doubt it would be anything electrical at this kind of age. The best thing to do would be to take it to a dealer and have them repair it. This truck must be still on warranty, no?

cruise control fuse is under the hood.
Take it back to the dealer.

Your fuel economy is bad, it's just the nature of the beast, and although you can spend a lot of money to make it a little better, in the long run the only help is to open the air intake up (K&N) and replace the exhaust system with a less restrictive flow (Flowmaster).
aside from that, these things cost a lot of money. Money that you won't get back just dealing with the poor MPG.

It's your choice!

Slantsixness