The 3,000-Mile Myth Check it out, and find the manufacturer's recommended oil change interval for your car. You may not have to change your oil every 3,000 miles.
For example, my 2003 Honda Accord LX only needs one every 10,000 miles. Add that to the fact that I just had my oil changed with Sastrol Synthetic Blend 5W-30, and Wal-Mart had it in 5-quart bottles for $7 for some reason. That, plus a FREM filter, cost around $12 total. (Yeah I know the manual SAYS 5W-20 for my car but it had 10W-30 in it from the last oil change and it didn't seem to hurt it, and this is closer to recommendation.)
Spiffy!
Help the environment! Quit changing your oil more than necessary, and remember to recycle your used oil! Just remember that you may need to change your oil a bit more often than listed, if you regularly do more strenuous driving, like off-road, heavily loaded, or in dusty areas.