I have a 2002 2500HD. Bully Dog Power Pup programmer set the extreme setting. I opened up the stock air box, tire pressure at 85psi in 245's.

In 2008, took a 500 mile trip over Thanksgiving. I drove 60mph both ways.....and yes it was horrible but wanted to see what mileage I could get running that speed.

I averaged 25.5 over the 1000 mile trip.

AND I WILL NEVER DO THAT AGAIN....HA HA!