Originally Posted By: Solarent
Originally Posted By: CrawfishTails
(Posting this over in the discussion of Base Oil Interchange rules and STM Single Tech Matrix guidelines too.) Its applicable to what I was trying to figure out was going on at Schaeffer Oil's tech data sheets here claiming exact 9.8 & 130% scores identically for all their motor oils. Still think this is fishy practice. Below, I think there is a valid reason for an oil company to only be able to say "PASS" if using STM with no actual engine tests, not exact figures! ---->
From
http://papers.sae.org/2002-01-2676/ :
"Once a guideline is approved, a supplier can interchange or read an engine test
pass for a particular additive package in a particular base oil and/or viscosity grade to a base oil and/or viscosity grade of equal or better performance
without running an engine test."
OK, so it sounds like a company can only claim an oil they didn't actually run through a Sequence IIIG for example "
passed", not the "all its oils magically" have the
same micron wear rating and viscosity increases.
I'm a little late to the party but here is my two cents:
Any blender purchasing a "pre-approved" DI pack relies on BOI and STM guidelines. How it typically works is the Additive supplier does serious amounts of testing and certifications with readily available base oils that their customers are using. The additive supplier also can provide sample formulas which all perform basically the same on certain tests to meet the various required viscosity grades.
When registering for certification, the additive supplier provides the blender with average results for the DI pack, and these can then be used to certify multiple grades. As long as these sample formulas (sometimes called oil studies) are followed, the oils can be registered with the API and do not require additional testing.
The fact that Schaeffer Oil have decided to publish their information (which is not typical) IMO is applaudable, but is likely based off of the results they received from their Additive supplier. Cam Lobe wear is primarily a function of the additives not so much the viscosity.
Great insight. Thanks! Agreed with almost all you say. However, I think you're missing the point, that exact Sequence IIIG results can't cover 5 oils, only "
test pass" will do. The STM rules were meant to show that a DI package can vary a little in performance in vastly diff base oils, syn to semi-syn, -20 to -30 weights, but not enough to cause a test fail. Just pass/fail is all they are allowed to
assume.
I do disagree a little that cam lobe wear is "mostly" additives. Tech papers I've read over the years show that heavier oils stay out of Boundary Lubrication (BL) more on cams. Lighter oils need additives to a greater extent, since more BL occurs, think Stribeck curves. Half additives, half viscosity from what I've seen, approximately, not purely one or the other. (Corroborated with a statement by a Castrol person on bitog too that RNT tests are hard to pass with light 0w-20 oils.)
I admit I merely form my opinion from tech papers over many years of engineering studies and statements from experts with direct lab experience in esoteric areas.