2004.5 Sierra 2500hd 13mpg?

[JGundersen]

I have a 2004.5 (LLY) GMC Sierra 2500HD with a cold air intake and 4" exhaust. I have only had the truck for a month but expected to get more than 13mpg's. What kind of mileage are other people getting with similar trucks?

[angelic0-]

What tire sizes are you running, and what gearing is it ?

 

with that CAI your MAF might be leaving the party !

[thearborbarber]

12.4mpg on average from my 2004 2500hd 4x4 with a 6.0 liter but you deisel should get closer to 20mpg empty. I would check fuel filter and water separator.

[pwall]

Welcome!

And as in the previous post, you should be getting at least 20mpg, if not better.

[JGundersen]

I have 3.73 gears with 33" tires and have changed every fluid and filter from the front of the truck to the back in the two months I have owned it.