I put gas in it yesterday, I know my odometer is off either from the gear change, tranmission swap (different speedo gears), or both, it says I drove 80 miles, but only used 1/3 of a tank, but I do know my fuel gauge is accurate. My manual says my car holds 18 gallons, but I've only ever been able to put in 16. I drove the same 1 mile distance (backed up by google maps, was exactly 1 mile distance) in two cars, dad's saturn reads 1 mile, as does google maps. My car reads 1.5 miles in the same distance. If my math is correct (probably not), that means my odo is reading 50% more than a "normal" car. I guess that means if I travel 50 miles in my car, it's actually 25.
SO.
I'm either getting about 15mpg, or 7.5. If it's 7.5, that honestly kinda sucks *ss. It's a bone stock 350 w/ mild cam with a qjet. I'd hope I was at least in the low double digits.