I know it's a lot of miles, and i'm getting the '1qt every 1k miles' of oil use(not 'loss' as far as I can tell.). Ideas why the cat may have gone bad? Had no codes, etc. Just massive power and mileage loss over a period of 15k miles, or so. Someone suggested the pcv could be dropping oil into the cat, causing it to heat up and block. Replaced pcv w/ no change in oil use, so- 'undertemined' I think, if the pcv is related to either oil use or cat going bad.