Greetings and thank you all for taking time from your day for this. I've been using synthetic oil in my Avalon since I bought it. It still runs like new which I some credit to the oil for that. I have replaced all the seals, valve cover gaskets and everything so there are no oil leaks. Been noticing lately that it goes through a quart of oil every 2k miles. Wondering if I should consider switching to non-synthetic oil now hoping it might slow down on burning oil.
Thanks in advance for your thoughts,
Jim
Piston rings don't care whether it's synthetic or conventional. When they're worn out, they're worn out.
If you're lucky it could just be valve seals, they're very likely to be hardened and cracking at that age. If you do a compression test on the engine it will give you an idea of the condition of the rings, though it is possible for oil rings to wear faster than compression rings in some engines.
I agree that the valve seals could be the culprit but question the logic of the rings since I haven't seen any decline in the performance of the engine. As I mentioned before, it's still running like new. I would think that if it were rings I would be losing compression and would at least see some smoke which I don't. Anyway, would I be wise to switch to regular oil?
Sometimes we don't notice the performance difference due to wear that occurs gradually over a long period of time. However a compression test will give you an idea of the overall health of the engine and if compression rings are worn you can bet oil control rings are worn as well.
With the amount of oil loss you describe you would not necessarily see visible smoke but there would be telltale oil residue in the tailpipe. Switching to conventional oil would only help if some or all of the oil loss is due to minor seal leaks, and if you have all new seals that would not be the case. If not leaking it's burning somewhere and that means either valve seals, PCV system, or oil control rings.
Have you changed the pcv valve?
Yes, the PCV valve has been changed.