Originally Posted By: gpshumway
Originally Posted By: JOD
Here's the TEOST 33C test protocol:
LINK
First off, folks can make a determination as to whether or not this set is relevant to their use. Given that I can't think of any turbos that currently spec 0W20, I'm having a hard time seeing it. I'm sure some will interpret this to mean that an oil that meets this spec is "better", since some people don't understand the basic principle of "suitability"--but that fact is, if you don't have a turbo, the results on this test aren't relevant unless you've got some serious mechanical issues going on...
Secondly, there's zero evidence that high VI oils leave more deposits, yet this gets tossed around as fact. I do find the relativism of proof to be pretty funny though: "just because it's published in some magazine doesn't make it proof" suddenly becomes "someone post a while back on an internet forum"... It's an interesting way to look at things...
This is a bit of a wall of text, my apologies.
Many assume that 0w20 can be safely used in any 5w20 application, so the fact that the requirements for 0w20 are less strict should become more common knowledge. Ford's new Ecoboost 1.6l specs 5w20 and probably shouldn't use 0w20 because of TEOST.
Turbochargers aren't the only place where oil sees high temperatures which can lead to deposits. VW TDI engines starting in ~1999 specified synthetic oil not because of the turbo, but because the rings were very close to the top of the piston to maximize compression, thus subjecting the oil to high temperatures and potential deposit formation. In more recent times I'm thinking particularly of Ford products with direct injection. Ford's proprietary spec is substantially stricter than GF-5, more like ACEA A1/B1 and none of the high VI 0w20 oils claim to meet A1/B1, though I think Fuchs Titan GT1 is "recommended for".
Speaking of ACEA standards, you're correct that there's no evidence that the high VI oils cause more deposits, but as I said, none of them claim ACEA A1/B1, while most of the lower VI 0w20 oils from major makers do. The biggest areas of divergence between GF-5 and A1/B1 are in piston deposits, wear and sludge, with A1/B1 substantially more strict. Is it possible, even probable, that the high VI oils actually meet the ACEA standards, but their makers choose not to certify them? Maybe, but all things equal, I'd select the oil that meets both GF-5 and A1/B1.
We should be clear that we're talking about more than one kind of deposit here, there are piston deposits, varnish/sludge and other deposits within the lubricated parts of the engine, and there are the oil's contribution to intake manifold, intake valve and combustion chamber deposits. The former is quite well controlled by the certification requirements, the latter is not.
Some question the relevance of NOACK, but if it weren't an important performance metric in many engines, ILSAC wouldn't have put it in the qualification program, and GM wouldn't have put even tighter requirements on Dexos oils. Any oil components which volitize will end up in the intake through the PCV system and will degrade the effective octane of the intake charge and possibly form deposits on the intake valves and combustion chambers. SOPUS chooses to use deposit formation as a differentiating factor for their top tier Ultra product vs other SOPUS products and their competitors. NOACK is part of that and SOPUS has stated that they also designed Ultra to burn cleanly which helps prevent combustion deposits.
Many of us who are crazy enough to read and post about motor oil on the internet are looking for performance beyond the minimum requirements of the specifications. As you correctly state, “better” would imply that one product is at least as good as another in every performance metric. Unfortunately that situation only happens in the real world if cost is not considered a performance metric. High quality oils represent the opportunity to allocate excess performance to areas which are most important to us. While there may be no direct evidence that high-VI oils cause more deposits, there is also no evidence that they reduce startup wear. Even if they do, that wear may not be relevant to the vehicle owner, as I said above, engines have outlasted bodywork since the days of GF-2 conventional 5w30. The only way we know high VI oils outperform their lower VI counterparts is in fuel economy, and the benefits there are incredibly small.
I say all of this having made a substantial effort to use the high VI Idemitsu oil in my Honda. I'm not opposed to ultra-high VI oils, I just think we need to be realistic about the benefits, mostly a teeny-weeny improvement in city fuel economy. They’re not the answer to every question, though many around here seem to think they are. They were originally designed for hybrid cars, which I suspect see substantially more variation in oil temperatures than regular cars due to stop-start and pure EV modes. This variation in temperature combined with the hybrid’s focus on fuel economy makes intermediate temperature viscosity unusually important in that application. Other combinations of car, owner and driving call for other oils.
Exceptionally well-written post. Clear and concise. Bravo sir
) for all to peruse.
