What all works on a little gas saving on the 6.2l?
I'm currently getting 12.5mpg

 

Nothing. It's a big engine in a heavy truck. Right foot discipline.

 

Install an uncooked egg on the gas pedal. Don't break it.

 

Tuners , air intakes, better octane fuels?
Nothing helps? I just need a few opinions before I wasted any money on trying these things

 

A tune, for economy, might help a little but the truck will be worn out before the savings pays for the tuner. The best thing is to drive for mpg. Ease off from stops. Coast instead of braking where possible and try to avoid idling.

 

i'd go for the tuner.
There probably aren't any tires available for your truck that are designed with low rolling resistance. But if there are, buy those next time.