I wouldn't call them polar molecules. These additives form chemical bonds and tribofilms, not just loosely attach to surfaces. The additives are usually not a variable unless you want to pour in some aftermarket ZDDP etc. However, the base-oil viscosity is. You're also talking about anecdotal experiences, which are subject to many sources of bias, on highly specific engines in highly specific operating conditions. Moreover, you blend your own oils, which brings many question marks such as additive compatibility and lack of thorough testing other than some racing events, which run the coolant only at around 60 Â°C and the oil only at around 70 Â°C thanks to specialized cooling. In addition to the Chevron brochure I posted above, there is a paper by Nissan that emphasizes base-oil viscosity for reducing the wear in timing chains: Nissan study on wear in timing chains Regarding ZDDP there is no evidence that now-obsolete oils with high ZDDP content resulted in less wear than modern oils. On the contrary it turns out that the opposite is the case. For this reason there is no direct relation between the ZDDP content and wear. However, there is a direct relation between the base-oil viscosity and wear. I have a thread on this, too: Wear and fuel economy results for selected SF through SN oils: PCMO3 engine test
Originally Posted by RDY4WAR
I know what asperities are. I've done a lot of cylinder honing, crankshaft polishing, and lifter bore honing. Even fine tuning a targeted asperity height, shape, and gap for specific applications. I was asking if you were saying the oil film in the gaps was more important than the polar molecules on the asperities. I can see where your argument is going, but it doesn't align with what I've seen with my own engines and others in the real world. Additive types and concentrations have made huge differences, but practically none observed with base oil changes. I feel like the activation of anti-wear additives in mixed and boundary lubrication is far more important than the base oil.