Re: Choice of oil

Posted by Owen_Dyneto On 2014/3/14 17:25:57

ZDDP is most essential for flat tappet engines with a high loading on the cam/tappet interface and no Packard engines within factory spec fall in that category. That said, might help and can't hurt applies.

Pat Green, there is a limit above which ZDDP becomes harmful to your engine, so adding it to oil that already contains it is something to be cautious about. Shell Rotella T already contains a pretty good amount of ZDDP, though less than the earlier CI-4 formula contained. The decrease from CI-4 to the current CJ-4 was from about 1380 ppm to about 1000 ppm. So I'd really be leery of adding more unless I knew how to determine a safe dose. Remember, with proper maintenance Packard engines ran to 100,000 miles or so long before ZDDP was ever introduced into motor oil (its use was an outgrowth of WWII).

Just as added info, here are some Zinc levels in other grades of motor oil, courtesy of Castrol.

SE-SJ - 1280 ppm
SL - 1180 ppm
SM - 940 ppm