What else can help?

[nuthinbutfords]

I am trying to improve my fuel economy. I am getting about 11.2 mpg on a 99 F250 on 37's with 3.73 gears. I just ordered the 6637 mod, and did and oil change with wix filter, and fuel filter change with a wix as well. I have clean and tightened my up pipes and found no leaks. Where else should I look? I keep my foot off the pedal. Thanks everyone for all the help you have given me so far.

[dazdillenger]

Keep the rpm's around 1750, boost in the LOW single digits-allow your speed to fluctuate a bit-drop a few mph uphill, gain a few downhill.

Other than that, a chip (I'd get an 80hp econo from DPtuner.com-jody knows his stuff) a 203 degree thermostat, free flowing exhaust, make sure the tires have 70+psi in them, and your hubs are unlocked if you have a 4x4.

My early 99 cclb 4x4 would get 20.7 unloaded on the highway at 59mph. I could go 740+ miles before stopping for fuel. That sort of driving took discipline.

[01Crewcab7.3]

Not too much will help, you're running 37" tires with 3.73's. If you were running like 4.56's or went down to say a 285/75/16 you would pick up several MPG's I'm sure.

[nuthinbutfords]

well more specifics on the truck.. It does have a F5 chip from Jody set on an economy tune. Also has a 4in downpipe in a 5in exhaust.

[dazdillenger]

My 99 had a 8.5" with 37's, and unloaded I could get 17ish. That was also with 373's.