Hello,
Since ZDDP is back in the discussion see note below from Shell.
I did put Rotella T in my '71 TR6. I have no relation or interest whatsoever
in Shell etc.
Regards,
Bob
"Bob,
With the introduction a couple of years ago of ILSAC specification GF-4 and
API specification SM for gasoline-only engine oils, the amount of
phosphorous in the oil had to be reduced to prolong the life of catalytic
converters. Zinc-based anti-wear compounds, which also contain phosphorous,
were reduced as well. These zinc compounds work well to protect flat tappet
engines from excessive wear, so the modern gasoline-only engine oils are not
as effective in this regard as they once were.
Diesel engine oils don't suffer from the same requirements to protect
catalytic converters, so the amount of zinc-based anti-wear additives
remained high. Products like Shell Rotella T Oils, which also carry API
S-series licenses for gasoline engines, have found favor for flat tappet
engines.
Shell Rotella T oils contain approximately 1200 ppm zinc. At that level,
Shell Rotella T Oils still have at least 50% more of these anti-wear
additives as most current gasoline-only engine oils. These levels of zinc
have historically offered good protection in flat tappet applications.
Thank you for your interest in Shell Rotella Products!
Regards,
Edward Calcote
Staff Chemist, Shell Lubricants US Technical Information Center
http://www.rotella.com/ "
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