I have flat tappets, but the pressures on it on the M119 engine are very low, so all the lobes are still flat. For older engines with high-pressures, I agree with dermapaint.
So far, I've been running Regane in the tank, so I'll report when I get more progress.
As for varnish, look at this:
http://papers.sae.org/2007-01-4133/
"Engine oils are subjected to a series of industry standard engine dynamometer tests to measure their wear protection capability, sludge and
varnish formation tendencies"
"...it was observed that engine oil samples collected from fleet vehicles after 12,000 mile drain interval showed
10-15 % lower friction and more importantly, an order of magnitude
lower wear rate than those of fresh oils."
"It was also observed that the composition of the
tribochemical films formed was quite different on the surface tested with the drain oils from those formed with fresh oils. The objective of this investigation is to demonstrate how the friction and wear performance changed with oil drain intervals."
Does anyone have this article?
It seems that tribochemical films (which I'm assuming possibly includes varnish films on surfaces) help protect against wear.
And, there's also these articles:
https://springerlink3.metapress.com/cont...pringerlink.com
http://onlinelibrary.wiley.com/doi/10.1002/ls.3010090402/abstract
Does anyone have copies of these articles? It seems MMO and other additives might remove antiwear films, but I'd like to read the articles for their conclusions....