Originally Posted By: FetchFar
Good discussion. A bit long winded, still good. 1 micron to 40 micron HARD particles do the damage inside an engine. This has never been studied enough. Common sense tells you that the hardness (cragginess) of those free-roaming particles have the ability to scrape out internal engine metal, not the relatively soft carbon, hydrocarbons, and carbohydrates in there.
To get the hard iron particles out, use a magnetic drain plug, then all you can do is hope your air filter gets most silica out. After all that, let the oil filter just clean up whatever it can. Enough said.
I would disagree with you here. You essentially have this completely backwards.
I agree that silica is ingested; not much you can do but try to filter it out at the intake.
But soot is actually genereated in the engine; it's not ingested. Soot (incompletely burned hydrocarbons) is one of the most abrasive things in an engine; moreso than the small metal particles of Al, Fe, Pb and Cu. Cr is fairly tough, but not like carbon, and Cr is rare; often only in 1 or 2ppm increments total for a UOA. Soot starts out sub-micron in size; really, really small. Only when it would agglomerate with other carbon/soot particles, would it become large enough to do damage. Once it would reach 5um or larger, it does become an issue. And this is where the add-pack comes into play. The anti-agglomerates (or if you prefer, dispersants), keep the particles separated and don't let them cojoin. So as long as your OCI is reasonable, then the add-pack will be healthy enough to keep the soot in suspension and apart. As long as that happens, the wear will be really low. Again, look over those studies and my "normalcy" article. The proof is right there for all to see.
Metal particles are hardly ever (pratically never) bigger than 5um, and even if they were, they would not show up in a UOA because 5um is the upper end of the effective range for that method of viewing the construct of the particles being observed. Metal particles typically start small, and stay small, because they do not possess an affinity to cojoin like soot does.
If you believe otherwise, then please show the data backing up your claim.
Here is what I see from my perspective:
http://machinerylubrication.com/Read/51/soot-oil-engine
http://machinerylubrication.com/Read/712/diesel-engine-oil-particle
Check out that site; lots of reading. I will note that I do disagree with some of Jim's assertions, but generally I think his conclusions are sound. I disagree with some statments about linearity of metals; he casts a broad net whereas I'd be more definitive.