Just pumped again earlier, 374 miles from 9.23 gallons which equates to about 40.5mpg. Lots of highway mileage. There's about another 2 gallon I could've driven... perhaps another 60-80 miles?
Sometimes driving technique helps in saving gas. Steady acceleration, driving in highest gear possible, slowing down but not stopping completely, etc. For your tune ups, regular oil change, check ignition system; spark plugs/wires, distributor cap and rotor and have a clean air filter. And then pump your tires up a little more than the recommended pressures, I have mine at 40lbs. front, 38lbs. rear.
I also pump from Chevron whenever possible. That extra $2-3 you paid is well worth it for the engine. My last smog check had 0% CO output. It also might just be a mental thing, but the butt dyno says gas at the more expensive gas stations (Chevron, Shell, 76) makes the car run more powerful.