drive more conservatively, get a tonneau cover, inflate the tires properly and make sure everything is aligned (squishy tires=more resistance=more power needed, same goes if they are out of alignment), and you'll see a boost. I run my tires 3-5psi over on roadtrips and I definately notice a bit more in my tank after my trip. (make the same trip from my house in li to school upstate like 10 times a year, so i kinda know where it should be at...)
gotta cover. recently got new tires but i will check my tire pressure forsure. and it could be cause i like goin kinda fast ^.^
most of my rides are local. to lodi stockton or elk grove. around 30miles max per time.