Originally Posted By: JohnnyJohnson
Originally Posted By: 69GTX
It is true that there's a 2007 mfg's fleet study that concluded engine wear rates were the highest early in the oil change interval. After 3K miles wear rates continued to decline until the oil was "officially" used up (TBN, TAN, viscosity, or other factors). Still,
the period of higher wear likely varies considerably between oils, engines, and duty cycle. Apparently, the protective, anti-wear chemical tribofilms get fully/partially removed from the application of fresh detergents following an oil change. One size doesn't fit all.
If that was true why wouldn't we all be running oil forever and just use an additive to take care of TBN/TAN?
It appears to be something that's not true but often repeated here on Bitog. Take a look at this thread:
https://bobistheoilguy.com/forums/ubbthreads.php/topics/4443010/1
Originally Posted By: Shannow
That paper keeps getting trotted out as proof of something that the paper never tested nor demonstrated.
They took a bunch of used oils, some of which were utterly shagged, had thickened excessivly and had poor TBN.
Then they use a contacting surface tribometer and measured the establishment of the tribofilms with new and progressively used oil. The used oil formed tribofilms on fresh metal surfaces quicker than fresh.
This is entirely to be expected, as the first part of the laying down of tribofilms involves partial destruction of the ZDDP/Mo into more reactive species...some additive companies put a lot of different elemental "variaties" in so that there are different points of activation.
So the oil with the most already partially reacted species in it produced the best tribofilms the earliest...exactly as expected.
The Used oil, excessively thick, wiht no TBN to speak of was not necessarily the best oil to have in the engine. Extrapolating the limits (surface tribometer) of this study INTO that realm is really stretching the bow a bit (well a lot).
And at OCI, the quote that you have provided assumes that ALL of the tribofilm is removed to fresh metal (not true, never seen anything on that).
As to the thought process...
https://bobistheoilguy.com/forums/ubbthreads.php/topics/4060600/1