Wheels and tires! I got a great deal on a set of Konig Helium wheels and Goodyear FuelMax tires. The stock 16" tires cost more, so downsizing the wheels saves money in tires. After tax and rebates, the wheels were only $150 for the set. Next time I buy tires I'll recover that completely.
Wheels 15*6.5, 40 backspace (oem 16*6, 53 backspace)
11 lb each vs 17 lb
Tires 195-60-15 (oem 185-55-16)
Same overall diameter, same driving rpm, +10 width, -2 lb, +?? mpg.
The oem tires (Dunlop sp sport 7000as) were junk. Poor traction and terrible tread life. This is the 2nd set this car has worn, completely finished at 64k miles. I know the FuelMax's are good, having run a set on the family Odyssey. They added (approximately) 1 mpg highway there, from 25, for a 4% increase over the already good Michelin Symmetry oem's.
I've dropped 32 lb overall, lowered my RRc, improved my acceleration and braking (slightly), improved rough-surface suspension handling (noticeably!), and improved traction and comfort.
Aerodynamics is a slight loss, with the very open spokes and a 3/4" track width increase. The wheels were really sunk in before, so they're still mostly covered by the body. Most of my driving is local "suburban" stuff so that's worth it to me.
Oh, and I got bronze color. I like the look of dark wheels, but the pure black I had before looks bad with weathered not-quite-black tires.