just a quick post, but for those thatdon't understand synthetic ol, the fact is it NEVER breaks down, in fact it just gets dirty, which is why we recycle oil and don't throw it away.

Now with non-synthetic oils it too will not break down, but new engines run hotter thus causing non/synth oil to coke up inside your engine, this is why you only run synthetic in new cars.


so to review;

oils never break down, they just get dirty, also the additive package within the oil becomes consume after 5-10k miles depending on how many quarts the engine takes.