Old Oil - really, really old oil...

[patrickt]

Originally Posted by 1ntCobra

Hmm, I used to be under the impression that you drove your Cobra more often than RodKnock, now I am not so sure.

As I've gotten older, I do tend to drive it less. Which brings about an interesting point, what crucial fact does a detailed oil sample not tell me? Everyone by now knows that if you have a solid flat tappet you have to be mindful of ZDDP levels in the oil. And how much ZDDP do you need? Answer: Enough. And it gets consumed as you encounter metal to metal contact. But that metal to metal contact just eats up your ZDDP, not your Zinc and Phosphorus numbers. So when I see an oil analysis that tells me that my used oil still has some really healthy numbers of Zinc and Phosphorus in it I still don't really know what my ZDDP numbers are now. I just know what they were when the oil was new. Kind of like if I split water in to hydrogen and oxygen. I'll still have the same amount of H and O2 that I did before, but I won't be able to drink it if I'm thirsty. And that's why with a SFT in your car you do need to watch the mileage in addition to the lab results. Or you can just wait until you see the wear metals start to go up and then say "ok, I should have changed the oil last time I had it tested."