Quote:
Originally Posted by c1800
Wow, there’s so many threads on multiple forums about oil. These 60’s engines require a reasonable level of zinc and phosphorus, somewhere around 1200 to 1300 ppm. Modern oils don’t have levels that high due to catalytic fouling. Do your research and the answer will be apparent. 10w30 vs 10w40 vs 20w50 depends on ambient temps. I.e. summer 20w50, winter 10 or 5 w 40 or 30. Depends on how cold it gets.
p.s. indiscriminate use of ZDDP additive can result in levels too high which will result in accelerated wear of cams.
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Yer on the right track by and large...
It isnt just ambeint temps, its the internal oil galleries, bearing clearances, oil pump etc which also govern the viscosity.
Zddp needs to be in the 800-1300 range, though classic oils ought to be 1000-1300 range. Yes, too much isnt good. Some modern oils still contain over 1200 zddp, which is generally those which are API SL rated as a mild rule of thumb. Some C spec oils contain 800 which is sufficient, A/B spec oils usually contain in the 1000-1100 region. IIRC, off the top of my head, at work...