Jeez, half-a-quart every 500 miles? You need new rings methinks. You could always swing by Wally world and try this stuff called Engine Restore. It comes in 4, 6, and 8 cylinder varieties, in a silver colored can. You add it during an oil change, and it should seal up some of the holes, maybe fix the problem. Just follow the directions and make sure that you check the oil frequently. Good luck.
