My dad has a 2003 F-350 4x4 with the 7.3 with 233k miles and he has been claiming that his fuel mileages isnt as good as it once was.. its up on 35x12.50-20 procomps and has 3 1/2 in down pipe to a 4" w/muffler. Basic superchip programmer and a drop in K&N.. I was thinking about upgrading him to a S&B Cold air to help with fuel mileages.. Do you guys recommend anything else I could do to help fuel? I heard something about maybe getting the turbo cleaned and propeller changed? hes getting 13-14 mostly highway and he used to get 16-18.. any advice helps, thanks

 

Skip the S&B, do a tymar intake (google it), and his MPGs shouldn't have dropped like that... need to find out whats wrong. Look for boost leaks (especially the intercooler boots), leaky up-pipes, broken EBPV sensor tube, etc.

 

That's why they say its always good to have a boost gauge. I'm on a f150 right now but as soon as I buy a turbo diesel I will forsure invest in a good boost gauge. Just so that I know the psi when it's new, and later on to see If it's stopes at all.