Doug, if you want to see a good example of M1 0W-40 not performing as well as other oils, spend some time looking at UOAs VW 1.8T engine. You dig them up; you are the one who wants to see evidence so bad. I have this engine (it's hard on oils) and have been analyzing the UOAs on it for years. It is clear after viewing lots of these UOAs that M1 0W-40 almost always gives higher iron wear numbers than other oils typically used in these engines. It does sheer quite a bit as well, without fuel dilution being the cause. After x amount of miles (somewhere around 5k miles), it starts to thicken up and by around 10k miles, the viscosity is about back to where it started (that does not meet my definition of staying "in grade" even though it meets ACEA A3's standard for that). Most other 5W-40 oils sheer similarly in the 1.8T (Amsoil 5W-40 appears to be exception), so we cannot single out M1 0W-40 for this trait. But 30 weight oils like GC and M1 5W-30/10W-30 and even Amsoil 5W-40 do not show this same sheering trend (in 5000 miles). Question is does sheering pose a problem? At least one study says that broken down VI improvers is a contributor to residual debris, potentially sludge precursors. You may choose to ignore that, but I see no reason to distrust that finding.
Now about the iron wear numbers in UOAs. In 5k miles in the 1.8T, typical iron wear number values with M1 0W-40 are about 17 ppm, while other top oils typically give about 10, 11, 12. That may not sound like much in those terms. Take the % difference to get a better feel for how much more iron is coming out of the engine (e.g (17-12)/12 = 41% more ppm of iron by changing to M1 0W-40 from these other oils). What "top oils" am I speaking of: 5W-40 versions of Valvoline Synpower, LubroMoly, Amsoil, Pentosyn. GC and M1 5W-30 also could be on the list of low iron wear oils in this engine. Maybe there is something strange going on with M1 0W-40 and all these extra particles are super tiny relative to the iron particles with other oils, so the UOAs are misleading. But there is no evidence to suggest that so cannot assume (maybe some particle size testing could settle that). And since M1 5W-30 usually gives less iron wear than M1 0W-40, I especially doubt any such mystery effect since the main difference those 2 oils is viscosity.
Then there are the high temperature tests I have done using M1 0W-40, Valvoline 5W-40, Castrol Syntec 10W-40, GC, Amsoil 5W-40, M1 5W-30, M1 10W-30 EP & non-EP, Valvoline Synpower 10W-30, and Redline 10W-30. I'll keep this as brief as possible, so will omit many details. The first two oils showed nearly identical resistance to thermal oxidation, sludge/deposit formation, and volatility. The latter is a Group 3 oil, as we know, and it actually gives great UOAs in the 1.8T. The point is M1 0W-40 is only equal to a Group 3 5W-40 oil in terms of handling high temps. It's not some oil with fabulous base stocks despite what Mobil tells us. The other oils listed above were all significantly more robust in my tests than the first 2 oils (including Amsoil 5W-40 and Syntec 10W-40 - both 40 weight oils). The general reason for the 30 weight oils doing well is that they start out with thicker base stocks and have less (or none) VI improvers. Amsoil 5W-40 likely outperformed M1 0W-40 and Valvoline 5W-40 due to superior base stocks (a good PAO) and possibly lower VI improvers amounts. GC (new Gold version) was particularly interesting because it has nice viscosity vs. temp characteristics and was still as equally robust as M1 10W-30 EP and slightly more robust than M1 5W-30. That indicates excellent base stocks in GC. Also of note is that Valvoline Synpower 10W-30 and M1 10W-30 performed the same in my tests, while Redline 10W-30 showed zero deposits/sludge and significantly less volatility than both preceding oils. Those ester basestocks in Redline sure can handle high temps. These tests were used to rank oils in various areas in extreme temps, not necessarily represent conditions inside an engine; an oil that beats another in these extreme temps will not necessarily show differences at 210 deg F, but the outcome certainly won't reverse. FWIW, the temperatures of a glowing red turbo are in the neighborhood of >1200 degrees F. Another FWIW, sludge/deposits can be left behind in an engine without ever showing up in the UOAs (and thus, part of the motivation for doing these tests). I have left out test details because it would take too long to write out here. If you don't want to believe my results, do some tests yourself.
Meeting lots of European oil specs is nice but it is possible to do so and still be outperformed by oils meeting those same specs (obviously) and in some case by oils that don't even meet those specs (e.g. M1 5W-30 beating M1 0W-40 in terms of wear numbers and sludge/deposit formation in the 1.8T). Man cannot live by oil specs met alone, is what someone said. Tests in those Euro specs are pretty stringent, but not amazingly so; they are looking for suitable oils, not trying to make them so only 1 or 2 unbelievable oils can meet them. Looking at a combination of MANY UOAs, specs met, and maybe even some home experiments tells a much better story about how an oil stacks up.
These shortcomings don't matter for the average car owner. M1 0W-40 will undoubtedly give long life to all or nearly all gasoline engines with proper drain intervals. I'm not saying it is a bad oil; it's just that there are better choices. I am saying that based on many UOAs and my own high temperature tests, it will not give as long an engine life as some other oils on an engine that is hard on oils. Not only is the 1.8T hard on oil, but so are the turbo Saab and Volvo engines.
BTW, I think it is low that you have quoted and challenged TooSlick as a main point of this thread. Work out that issue with a therapist or something, not on here.
Now about the iron wear numbers in UOAs. In 5k miles in the 1.8T, typical iron wear number values with M1 0W-40 are about 17 ppm, while other top oils typically give about 10, 11, 12. That may not sound like much in those terms. Take the % difference to get a better feel for how much more iron is coming out of the engine (e.g (17-12)/12 = 41% more ppm of iron by changing to M1 0W-40 from these other oils). What "top oils" am I speaking of: 5W-40 versions of Valvoline Synpower, LubroMoly, Amsoil, Pentosyn. GC and M1 5W-30 also could be on the list of low iron wear oils in this engine. Maybe there is something strange going on with M1 0W-40 and all these extra particles are super tiny relative to the iron particles with other oils, so the UOAs are misleading. But there is no evidence to suggest that so cannot assume (maybe some particle size testing could settle that). And since M1 5W-30 usually gives less iron wear than M1 0W-40, I especially doubt any such mystery effect since the main difference those 2 oils is viscosity.
Then there are the high temperature tests I have done using M1 0W-40, Valvoline 5W-40, Castrol Syntec 10W-40, GC, Amsoil 5W-40, M1 5W-30, M1 10W-30 EP & non-EP, Valvoline Synpower 10W-30, and Redline 10W-30. I'll keep this as brief as possible, so will omit many details. The first two oils showed nearly identical resistance to thermal oxidation, sludge/deposit formation, and volatility. The latter is a Group 3 oil, as we know, and it actually gives great UOAs in the 1.8T. The point is M1 0W-40 is only equal to a Group 3 5W-40 oil in terms of handling high temps. It's not some oil with fabulous base stocks despite what Mobil tells us. The other oils listed above were all significantly more robust in my tests than the first 2 oils (including Amsoil 5W-40 and Syntec 10W-40 - both 40 weight oils). The general reason for the 30 weight oils doing well is that they start out with thicker base stocks and have less (or none) VI improvers. Amsoil 5W-40 likely outperformed M1 0W-40 and Valvoline 5W-40 due to superior base stocks (a good PAO) and possibly lower VI improvers amounts. GC (new Gold version) was particularly interesting because it has nice viscosity vs. temp characteristics and was still as equally robust as M1 10W-30 EP and slightly more robust than M1 5W-30. That indicates excellent base stocks in GC. Also of note is that Valvoline Synpower 10W-30 and M1 10W-30 performed the same in my tests, while Redline 10W-30 showed zero deposits/sludge and significantly less volatility than both preceding oils. Those ester basestocks in Redline sure can handle high temps. These tests were used to rank oils in various areas in extreme temps, not necessarily represent conditions inside an engine; an oil that beats another in these extreme temps will not necessarily show differences at 210 deg F, but the outcome certainly won't reverse. FWIW, the temperatures of a glowing red turbo are in the neighborhood of >1200 degrees F. Another FWIW, sludge/deposits can be left behind in an engine without ever showing up in the UOAs (and thus, part of the motivation for doing these tests). I have left out test details because it would take too long to write out here. If you don't want to believe my results, do some tests yourself.
Meeting lots of European oil specs is nice but it is possible to do so and still be outperformed by oils meeting those same specs (obviously) and in some case by oils that don't even meet those specs (e.g. M1 5W-30 beating M1 0W-40 in terms of wear numbers and sludge/deposit formation in the 1.8T). Man cannot live by oil specs met alone, is what someone said. Tests in those Euro specs are pretty stringent, but not amazingly so; they are looking for suitable oils, not trying to make them so only 1 or 2 unbelievable oils can meet them. Looking at a combination of MANY UOAs, specs met, and maybe even some home experiments tells a much better story about how an oil stacks up.
These shortcomings don't matter for the average car owner. M1 0W-40 will undoubtedly give long life to all or nearly all gasoline engines with proper drain intervals. I'm not saying it is a bad oil; it's just that there are better choices. I am saying that based on many UOAs and my own high temperature tests, it will not give as long an engine life as some other oils on an engine that is hard on oils. Not only is the 1.8T hard on oil, but so are the turbo Saab and Volvo engines.
BTW, I think it is low that you have quoted and challenged TooSlick as a main point of this thread. Work out that issue with a therapist or something, not on here.
