I installed new spark plugs (NGK Laser Iridium), I have noticed a 2 MPG gain as well as better performance. Here are photo's of my old spark plugs with 65,500 miles on them
Those are pretty rough looking, it seems like your engine might be running a little rich...next time you change them (hopefully a little sooner!), keep an eye on the color. If they're still burnt up looking (btw, white would be lean), I'd do a full tune up to make sure everything is flowing how it should.