I'm only going to reply to those issues where I think you are way off base here.
Originally Posted By: dnewton3
The study clearly states that a GF-3 "factory fill", a GF-4 "factory fill" and a prototype GF-5 were used. Sir, factory fill fluids are NOT "non fully formulated", as you claim. They are produced for consumption by the end user and are, in fact, in a state of full add-pack as delivered for use. Additionally, when the study was written, the "prototype" GF-5 has since become the fully-formulated product that is now their offering. It was only a prototype then as they were not yet offering GF-5 yet. But what was "prototype" then is in the bottle now, so ALL THREE LUBES were essentially as one can purchase then and now, and are in fact "fully formulated".
Yes, the SAE article under discussion did use fully formulated motor oils.
The following words are from the quoted articles, not this study. Those articles are using non fully formulated oils to study the effect of the additives individually. This is the source of the mistaken idea that new fully formulated oil removes the existing tribofilm put in place by a fully formulated oil.
Originally Posted By: SAE
Fujita et al. demonstrated that the thickness of the lubricant-derived film increases steadily with test duration and stabilizes at the 50-100 nm level. The thickness is almost independent of phosphorous concentration (2). Film thickness is also dependent on oil temperature with higher temperatures tending to promote greater film thickness (3). However, when a dispersant is added, the film is removed and the film thickness stabilizes at a lower value. The antagonistic behavior of dispersants is well-known and one of the possible mechanisms was believed to be the competition between the dispersant and ZDDP molecules to adsorb on available surface sites.
2. Fujita, H., Glovnea, R.P., and Spikes, H.A., "Study of zinc dialkyldithiophosphate antiwear film formation and removal processes, part I: Experimental", Trib. Trans., 2005, 48, pp.558-566.
3. Taylor, I., Dratva, A, and Spikes, H.A., "Friction and wear behavior of zinc dialkyldithiophosphate additive", Trib. Trans., 2000, 43(3), pp.469-79.
Originally Posted By: Authors of this SAE paper
it points to the fact that once the film is formed with a fully formulated oil, it is not removed very quickly. The existing film may affect the chemical mechanism for forming the new film which provided the reduced friction and wear rate benefit.
Originally Posted By: DNewton3
Close; they ran them to 15k miles; maybe that was a typo on your part?
Yes, as was Cobalt 66. It's Cobalt 56.
Originally Posted By: edhackett
... the new oil was always run on new parts. They had not undergone the break in that valve train parts undergo. The used oil was always run on broken in parts.
Originally Posted By: DNewton3
No sir, that is not correct. Quoting the study:
"A different cam lobe and a tappet shim were used for each oil." Now, the study does not specifically state if the cam and tappets were new or broken-in, but it does CLEARLY state that each lube had a different part-group introduced. To me, the inference I take is that rather than stacking the wear induced from all tests onto the same single cam/tappet, they used a "new" (not brand new, but unique in that each had not been previously utilized in testing) set of parts for each oil. Each time they swapped oils, they set it up with a different lobe/tappet. Whether or not these were "new" (versus broken-in) or not, the variability you infer is not present. Each lube got a unique (and presumably reasonable equal) lobe/tappet set up.
See figure 4, where they refer to the shim used with new oils as "fresh" or "used". The nature of the test would preclude any break-in as the oil used would leave traces of a tribofilm that would interfere with their results. If the intent of the experiment was to evaluate wear, each run of every oil should have been on a "fresh" shim. These were cobalt 56 doped parts and very expensive. Each oil got a shim and rocker. The new oil was always run on the "fresh" shim. Subsequent runs had the benefit of 100 hours of run in from fresh and the residual tribobilm that they stated remained after their cleaning procedure between runs.
Cobalt 56 has a half life of 77.27 days. There would be no used parts kicking around. Two runs of the same oil on the same shim about 2.5 months apart would result in half the wear being observed. Used could be taken as conditioned(broken in) just before use, but see above about not wanting an existing tribofilm.
Originally Posted By: edhackett
The second main uncontrolled variable is that since this was a bench test the new oil was never mixed with the used oil that carries over in an OC or exposed to new combustion byproducts. It remained "virgin" throughout the test, unlike what happens in the day to day operation of an engine.
Originally Posted By: DNewton3
I don't disagree here, but I do question your point? New oil is new oil. As soon as it would be mixed with carry-over (redisual) oil, then it's no longer "new". Each engine (and each person whom maintaines that engine) is going to exhibit a different level of how much residual is left to be mixed into the new oil. That is inescapable. However, residual oil is a bit of an overblown thing. It's unavoidable, and generally harmless.
The point is that the fact that the very thing that makes for a better triboflim is happening in an engine and not on the test bench brings the applicability of the bench test results into question when it comes stating new oil causes more wear in an engine. It's a very very long stretch to make the logical jump that 100 hours of operation without being exposed to normal aging equals 100 hours in an engine. It would appear that not only is the carry-over generally harmless, it appears it could be of benefit.
Ed