[quote=“Patton” post=67267]Scott, surprised in a good way or bad way?
RP[/quote]
Bad. Any diesel oil rated for “mixed fleet” operations will have enough anti-foam additive for our high revving use. But about 5yrs ago oil OEMs were in the decision making process of going for the CJ spec or staying with the CI spec. At least that’s what I think the specs were called. The CI spec allowed more ZDDP. This decision was more marketing then engineering. The marketing department wanted to be able to emblazon the bottles with the decal of the latest spec, and the science linking ZDDP with failed cats, the reason later oil certs contain less ZDDP, was never strong. I’m not saying that the EPA is wrong, I’m just saying that there doesn’t seem to be much consensus.
I used a couple CI+ oils, Valvoline Premium Blue among them, and then sent them out for oil analysis. The results came back kinda low on ZDDP. The problem was that a year had gone by between the article being published in TDR and me buying the oil. Oil additive packages change routinely, and we’ve no good way to stay ahead of that other than oil analysis. Oil OEM websites can easily be a generation or two behind on their published oil specs. Vavoline was probably going after a CJ cert and therefore reduced the ppm of ZDDP in their oil. No big deal for a modern engine with little valves and light springs, but a problem for older 2 valve engines and their heavy springs.
IIRC the sweetspot for ZDDP is 1250-1400ppm. Less is ok for a 4 valve motor, more is ok for a break-in oil.