L31MaxExpress
I'm Awesome
My 97 Express managed 18-19 mpg with the 350. Stock, tuned, cam, headers, 10 bolt 3.42 to 14 bolt 9.5 with 3.73 from 60E to 85E it never changed much. 5.13s did knock it down about 1 mpg, turning 3,000 rpm @ 75. I put the 3.73 10.5 14 bolt in it with the 383 and when it had the Rhoads V-Max lifters, made a ~500 mile road trip that managed 20.6 mpg. Best I have ever seen out of it. Removing the rhoads lifters and installing the marine intake killed mpg by about 3 mpg. Best I have seen since is 17-18 mpg. Wind even a crosswind and rolling grades can kill mileage off a bit. Alignment, brake drag and tire pressure can also drastically effect mpg. About 5 years ago, I had a brake hose collapse internally, slightly hanging the RH front caliper, warping the rotor that caused a slight front end vibration and cost 3-4 mpg on the highway. The rotor was not smoking hot either, but the wheel was about 50*F hotter than the LH side after about 1 hour on the road.