[Kolyan2k]

Originally Posted by CirrusSR22

For what it's worth, the general consensus on BITOG is that synthetic oil does not lubricate any better than non synthetic. They say the longer OCIs and the better cold flow properties are really the only advantages in a normal street car. Hot running turbo engines would benefit more though, but most engines don't run that hot.

Even the E36 SI (service interval) system takes mid-1990s non-synthetic oil (API SG & SH) up to 9,000 miles between changes. The current API SN standard Is significantly superior to those oils. I wouldn't be afraid to run a non synthetic API SN oil in an E90 up to nearly 10,000 miles. I'd be a little more hesitant to go that far in an N54, but certainly not an N52.

If I had an E90 I'd be glad to run a non-synth API SN oil to 7,500 - 10,000 miles and post an UOA.

suppose this is true and you can run regular oil for say 10k miles.....wouldn't it be true then that you can run synthetic oil for 20k miles or more ?

[CirrusSR22]

Originally Posted by Kolyan2k

suppose this is true and you can run regular oil for say 10k miles.....wouldn't it be true then that you can run synthetic oil for 20k miles or more ?

Kind of, but I wouldn't say synthetic is twice as good as an SN non-synthetic. Meaning that a synthetic OCI wouldn't always go twice as long. It'll go longer, for sure, but even non-synthetic SN is still a HIGHLY refined, "nearly" synthetic.

There are just way too many factors for anything to be certain either way.

I'm thinking at one point Mobil was claiming their top oils were good for 25,000 miles. They have long since changed their minds, and probably for good reason. They will only commit to 15,000 miles now on even their Extended Performance line. You'd need near ideal conditions for even the best synthetic to go over 20,000 miles.

Reading the UOAs on BITOG is always interesting, and I don't think I've seen many "good" UOAs over 20,000 miles. I think the only good ones were changing oil filters numerous times.