crankcase oil analysis

[olddog]

I must point out that depending on what you are looking for in the oil, the way you take the sample could add a lot a variability. Leave oil set and the heavy stuff sinks and the light stuff goes to the top. It is very possible that the lab correctly measured two samples from the same oil with different levels of what ever, due to segrigation.

[patrickt]

Originally Posted by olddog

I must point out that depending on what you are looking for in the oil, the way you take the sample could add a lot a variability. Leave oil set and the heavy stuff sinks and the light stuff goes to the top. It is very possible that the lab correctly measured two samples from the same oil with different levels of what ever, due to segrigation.

Oil sample taken in the identical fashion -- after a drive, via suction through the dipstick hole, tube placed the same distance down so that the sample came from the middle of the oil pan (not the top of the pan, not the bottom of the pan).

My Zinc and Phos. numbers varied widely; so widely that I wondered whether the ZDDP would "pool in clumps" and thus miss the sample pickup but nonetheless bond to the iron and steel as it went through the system. I don't know. I gave up on playing that game and instead use Brad Penn with a bottle and a half of EOS. BTW, the virgin sample of the BP that I sent in came back with low Zinc and Phos. numbers as well, but some other forums had users that had the identical experience with that particular lab. IOW, that lab tended to low-ball the ZDDP numbers.

[vettestr]

Maybe ignorance is bliss but I want to hold the reports to a higher value. I have used a couple of labs over the years but have always found consecutive reports within expected values. Oil analysis is a tool that adds light to an otherwise dark area and I find it useful as do many. I thought they were accredited by a few agencies and after checking I see they are or at least the ones I used.

[patrickt]

Originally Posted by vettestr

I thought they were accredited by a few agencies and after checking I see they are or at least the ones I used.

That "accreditation" involves payment of a membership fee -- nothing more (what, you think somebody actually flies out and checks the labs in person?). But like I said, I send my oil off to have it analyzed, and have done so for years.