Summertime, on a 300 mile round trip I would average right at 30 mpg; some days I could get it to 32 mpg. My trips back and forth to work (38 miles round trip) I usually avg 27-28. Wintertime, currently 23 mpg, and that is with it idling in the driveway for 10 minutes of a morning. I average 325 miles to a tank, but I could stretch it further. I usually fill up with 89 octane when the fuel gauge is a mark below 1/4. Car is a GT with 133K miles. Originial plug wires and fuel filter.