| [GMCnet] Subject: Re: Synthetic oil. Just some though's [message #282341] |
Fri, 17 July 2015 13:40  |
Botts Chuck
Messages: 43
Registered: May 2015
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"Oils For Older Flat Tappet Motors
Because all our GMC motorhome motors, except the newest Coop
remanufactured motors, have flat tappets, we cannot use the new
cleaner oils that have reduced the level of ZDDP (Zinc dithiophosphate)
in oils, because that ZDDP will clog catalytic converters. Those
oils are identified with the sunburst symbol for ecology purposes.
Catalytic converters are used to burn the residual gas in the
exhaust to meet ecology standards. No gasoline motors made after
1990 have the flat tappets that require 1,300 parts per million
(ppm) or higher levels of ZDDP to survive. Older classic flat tappet
motors started to fail when ZDDP in the oils was reduced to below
1,000 ppm.
I made a list of the oils that have acceptable levels of ZDDP for
our GMC motor use. That list was published in the GMCWS technical
notes. The oils that should not be used have “Energy Conserving”
written in the API “donut” on the bottle.
The best oils for flat tappet motors today are synthetic, like 15-
50, which does not meet the environmental clean oils standard. After
the 20,000-mile break-in on our new Co-op motor, I switched to all
synthetic oils in my GMC and also added ZDDP by using 4 oz of
Schneider racing cams formula 3 for both our flat tappet motors."
Page 44 in my book 240,000 miles In Small RVs
A lot of Flat tappet motors started failing when the oils were changed to reduce their ZDDP level below 1,000 parts per million to save from clogging the catalytic converters. Schneider Racing cams developed their formula 3 to protected their flat tappet racing cams. ZDDP was originally added to oils to leave a lubricant film on the wear surfaces during initial start of an motor.
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