Originally posted by McGyver
View Post
Nothing outside a race engine with high ramp pressure is going to be exceeding the shear strength of oil film (assuming the oil is relatively fresh and of good quality). The oil film prevents the metal-on-metal if the car is driven on a consistent basis. A standard M20 running 3,000 mile change intervals just doesn't generate the kind of pressure where ZDDP will truly come into play. An oil with a stable viscosity index and high shear strength that generates good pressure hot and cold will be more important.
Everyone jumped on the ZDDP bandwagon, myself included, because it's the easy thing to do. If it helps cover me because my camshaft maker didn't harden a batch properly or because the hard chrome on my rebuilt rockers isn't 100% or because the 356 A engine we just built makes shit for oil pressure because it's an inferior design that was inferior when new but now has sixty years of wear on it. But for an e30 with a stock camshaft and stock rockers, it's just not necessary.
Also, another reason modern oils have less ZDDP because the phosphorus loads up cats. Supposedly.
I did a ton of research and talked to petroleum engineers to choose a break-in oil and "normal" oil to use in my air-cooled Porsche builds. Our break-in oil has a healthy amount of ZDDP and the oils we use and recommend do too, but we're covering our ass on cars that may sit for months at a time. I'm interested in reducing first start-up wear after long-term storage by a client who's not particularly car savvy and won't crank to build oil pressure. We never use ZDDP additives in our own builds with the exception of the additive blend extant in the assembly lube.
Comment