You are correct, anything above a 10w30 (like race oils) is exempt from the low phosphorus requirements of API SM/SN. If the OP wants to run a 10w30 with high zinc, a diesel oil is gonna be his best bet IMO. Or find some pre API SM oil south of the border....
Originally Posted by paoester
Not 40 and 50 weight ones. Example: Mobil1 15w50 is SN and has high zddp, 1200 ppm, up there high. Cheap in 5 quart jugs at walmart. (The M1 0w40 at walmart would also work well in this application, another SN oil at 1000 ppm zddp, somewhat high.)
Originally Posted by Mad_Hatter
SN rated lubes for pcmo's are gonna have the zinc capped no matter the brand. Find a diesel 10w30 like Motorcraft Super Duty if you want higher zinc.