That information means zero to how an oil performs inside an engine. Those tests were not conducted according to industry standard ASTM methods. The Forester and WRX come from the factory with a very thin 30 grade (or even a thick 20 grade) Idemitsu oil with boosted levels of molybdenum and ZDDP. The BRZ/FR-S factory fill is also Idemitsu, but the viscosity is slightly lower and the ZDDP is lower as well.
That said, any Resource Conserving xW-30 is just a bit more robust than most xW-20's but the operational HTHS and operational viscosity (and possibly oil pressure) of the xW-30 will actually be very similar since many xW-30's shear in viscosity to a 20 grade oil in severe conditions (this is why Mobil1 0W-40 is a better choice than M1 5W-30 for some applications).
As far as ZDDP goes, M1 0W-20 EP, 5W-20 EP, 5W-30 EP all have the same levels. Both the 0W-20 AFE and 0W-30 AFE have lower levels of ZDDP.
http://www.mobiloil.com/USA-English/...duct_Guide.pdf
The viscosity of the M1 5W-20's is just a bit thicker than the viscosity of the 0W-20's. The 5W-20's should be more stable as well since more viscosity modifiers are needed for 0W-20's and 5W-30's.
German Castrol is a very thick 0W-30 (and not Resource Conserving) and is thicker than any Mobil1 xW-30 at 100C, with Mobil1 10W-30 High Mileage being the closest to GC.
And some comments regarding the above link:
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he's using one parameter that if you reach it you have already failed in lubricating your engine to state that any given oil is better than any other.
His testing method is not representative of any place in any engine that you or I are ever going to see.
And his conclusions have absolutely nothing to do with the parameter of choice by which he ranks them.
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That statement makes absolutely no sense whatsoever. Testing oil in a running engine allows you to observe the actual characteristics of the lubricant in its designed operating environment. This means it has to deal with fuel dilution, contamination, acids/combustion products, varying levels of heat. It has to resist deposit formation, it has to resist baking into varnish, it has to be able to neutralize the acids and do this for whatever the designed oil change interval is.
NONE of these things are replicated by this testing machine. NONE of them. Because it represents a scenario that no engine will ever see: Extreme sliding interface pressure, the closest relation to which would be the cam lobe/lifter interface on a flat tappet engine or a diesel injector/cam interface which never see those types of pressures, ever. So where's the relevance?
If this type of lubricant testing made sense, the OEM's would be all over it. It is inexpensive; certainly FAR cheaper than building an engine, running it on a dyno for hundreds of hours and then tearing it down and meticulously inspecting and measuring every component. But they aren't. That should speak volumes as to the true relevance of this testing methodology.
His actual testing and the results are certainly done with the utmost care and I have no doubt in my mind that he followed the scientific method to a T. I'm not questioning his testing or the results. I'm sure the results are wholly and entirely accurate and were obtained following proper procedures. And they represent exactly what he says they do: The failure point of the film strength of the oils tested. They don't however in any way translate to the actual conditions experienced by oil in an engine, only testing in an actual engine does that. That's why tear-downs are performed. That's why millions of dollars are spent by OEM's doing just that. And that's why companies like Mercedes, Porsche, BMW....etc maintain lists of tested/approved lubricants for use in their engines. If they could just Timken-test them to get that information they'd be making a lot more money on their approval process.
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http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=3124298
-Dennis