[gpshumway]

Originally Posted by viscositosis.rex

With regard to relatively thick ester based oils, why does RedLine have high fe numbers and Motul low, low fe numbers? Is it the scavenger effect?

I wouldn't say there's a big difference between the two. Remember there are severe limitations on what particle sizes show up in UOA. Also different driving conditions have a huge effect on Fe numbers. I doubt there are enough samples to make a useful comparison between the two, though I'm willing to be proven wrong. Redline certainly hasn't shown high Fe in my WRX. High copper, but not Fe.

With regard to groupIII+ oils, why does relatively very thin Sustina and TGMO run so clean, and shear so little? Why does thin MGMO shear with high amounts of moly in the oil.
With regard to deposit control, why does groupIII Castrol with a moderate NOACK score better than Amsoil in the TEOST? Don't we need to be smart about NOACK as well as VI/VII?
With regard to driving a BRZ/FRS is the goal good track times and also passing a smog check?
Wouldn't it seem that a thin GF6 compliant GTL oil would be the answer?
Just asking-in a whispered tone of voice.

Run clean? You mean stay the same color? Color is in no way indicative of oil quality, some additive packages darken quickly, others don't.

As to shear, be careful, you need an oil sample in the 1,000-3,000 mile range to really know. Shearing reduces viscosity, but oxidation, volatility and soot inclusion increase viscosity. Shearing happens soon in the OCI and then the other factors catch up, just because the oil came out of the engine the same viscosity it went in 5,000 miles ago doesn't mean it didn't shear. An oil which doesn't shear should get thicker by the end of the OCI. See my last run on Redline 5w30 in the NASIOC link above.

What would moly have to do with shearing? The Mazda oil shears because it's chock full of shear-prone viscosity index improvers.

NOACK is a general indicator of the quality of a base stock, that is a base stock with a narrower bell curve of molecular weights will have a lower NOACK than the same viscosity base stock with a broader molecular weight distribution. NOACK of a finished oil can be tricky though, some additives can actually reduce NOACK below that of the base stock, others increase it, it's simply one factor to consider.

The TEOST 33C deposit test is one of several deposit tests in the API/ILSAC sequences. Since we don't know how the oils performed in the TEOST MHT, Sequence IIIG, or Sequence VG tests, it's impossible to make an evaluation of the relative performance of those oils when it comes to "deposits" generically. Redline did very poor in that test, despite base stocks which stand up excellently to high temperatures, most likely due to the high levels of moly which can be problematic in turbochargers.

I don't know that GF6 will really change the calculus much it'll be a useful incremental improvement, but nothing a good GF5 oil won't provide.

In the end, I think the best way to evaluate an oil is by the performance specs it meets. The oil in discussion here, M1 AFE, is the only 0w20 I know of claimed by its maker to pass the Ford 5w20 specs, which means it passes the TEOST 33C requirements that are not required of 0w20 oils in general. Dexos, and ACEA A1/B1 are also specs that add to the confidence that the oil performs well.