I now get 13.5 MPG in my Hummer. With the price of diesel and my being a Hummer owner on a budget (talk about an Oxymoron), I would like to improve it's mileage. First off is to ditch some weight, I think I can get rid of 800 pounds by swapping the hardtop and steel doors with a military soft top and canvas doors. I now get 13.5 MPG so say the weight drop gets me 1 MPG, I would then be at 14.5. I like the idea of C precups and some head porting. I am confident that any power loss from switching to C precups from J precups would be cancelled out by the weight loss. So if I gain 2 MPG with the C precups, then I get to 16.5. My goal is 18 in a 6000 pound Hummer, right now it is 6800 with hartop.

I may experiment with the airflow tabs from http://www.airtab.com/ The hummer is atrocious when it comes to airflow, one of the worst aerodynamic designs ever, so I could pick up a little there.

Does anyone know if the diesel depot cam is worth any mileage improvement?

I am also thinking of more drastic weight reduction including removing the trailer hitch, factory airlift hooks and brackets, swapping the steel rims and runflats with aluminum wheels, sythetic winch line instead of steel, and swapping the heavy duty rear bumper with a light duty one. I think the additional mods will be worth 400 pounds of weight reduction, so I may get to around 5600-5800 depending on what I put back in like tools, etc. The 6800 is with spare tire and a few tools, but I will be adding more tools.