I have been trying to make adjustments to my engine to improve gas mileage, but with minimal success. The most recent road trip was 750 miles with about 2/3 interstate and the rest mostly good 2-lane highway. Overall on the trip was a shade under 15 mpg. I run about 75-80 on the interstate and 65-70 on 2-lanes generally with the AC. Engine is a 350 with iron vortec heads and a quadrajet. Transmission is a 700R4 with 3.73 rear gear. Likely a pretty common setup. The rpm is about 2600 at 80 mph. I'm curious if 15 is about what most of you get with a similar combination. If so, I will quit messing with jets, timing, distributor curves, etc and just go with it. Thanks for any comments.

Mark