Here's a tip for slightly increase your fuel efficiency. Where I live in Wisconsin we usually have three grades of gas: 87, 89ish, and 91ish. The 87 usually costs about the same as the 89 and sometimes it's a few cents more. The reason is that the 89 has up to 10% ethanol, which has the same effect as increasing octane. Ethanol is cheaper because it's subsidized by the government so much. Anyways, if you get the 87 that doesn't have ethanol it actually gives you slightly more power and slightly better fuel efficiency than the stuff with ethanol. I think ethanol has about 20-30% less energy than regular gasoline, so if 10% of your gasoline is ethanol, that means 2-3% less energy. In my Dodge Neon I can tell about 1mpg difference between the two. Usually 32mpg with ethanol, 33mpg without (highway).
By the way, I'm not sure that all gas stations put ethanol in the 89 but not 87, but some gas stations actually have it specifically marked. I go to those ones.