I'm very interested, but curious why the VOA on the 15w-50 shows low ZDDP. I saw a mention of 1371, wondered why the disparity. Need it for flat-tappet engines, so that number is important. Please clarify...
So far I've noticed is a correspondence between ZDDP and quiet running on my bikes. Mobil1 V-Twin (11/qt) is quietest, has something like 1600 ZDDP, then Valvoline ZR-1 dino (7/qt) is next in quietness with around 1300. I have some Brad Penn to try yet and some of the Syntec for vintage engines, just need to ride more so I can test them all out.
Quate, Crepa, Rota