<VV>High Mileage Oil for our engines
corvair at fnader.com
Sat Dec 8 22:06:29 EST 2007
*Antiwear Property Changes *
Another change that occurred in passenger car motor oils with GF-2 and
GF-3 is a more stringent limit on phosphorus, which is part of the zinc
phosphate (ZDDP) antiwear additive. The auto manufacturers are concerned
that phosphorus will deposit on surfaces of the catalytic converter and
shorten its life.
This is a complicated issue, and the deposits depend on the specific
ZDDP chemistry and the finished oil formulation. The industry was
unsuccessful in designing an engine test for an oil’s catalytic
converter deposit forming tendencies. Therefore, the auto manufacturers
set an arbitrary limit for motor oil of 0.1 percent phosphorus.
Antiwear additives are important in the absence of a hydrodynamic film,
such as in the valve train. The antiwear additives are activated by
frictional heat, which causes them to react with the hot surface and
form a chemical barrier to wear.
The mechanism by which phosphorus deposits form on catalytic converter
surfaces is not fully understood. It does not correlate directly with
oil volatility or oil consumption. On the other hand, if engine wear
causes oil consumption to increase, the risk of forming phosphorus
deposits in the converter would increase dramatically. It seems that
preventing wear and oil consumption should be a priority.
In the past, oil formulators could make a premium product by simply
adding more ZDDP. A similar move today would result in an oil
formulation that would not support new car warranties.
Bill Elliott wrote:
> It's emissions related. Lower ZZDP = lower emissions.
> John Beck wrote:
>> I don't doubt what you say Bob but, I'm curious why there's a
>> relationship between energy conserving and ZDDP content. I thought that
>> the star burst logo just refereed to a viscosity similar to weak
>> coffee. --J.B.
>> BobHelt at aol.com wrote:
>>> In a message dated 12/8/2007 4:53:24 PM US Mountain Standard Time,
>>> HallGrenn at aol.com writes:
>>> won't last as long with the SM oils.
>>> Hey, don't give SM oils such a bad rap. SM oils are the only currently
>>> available oils that have no upper limit on the amount of Phosphorous
>>> as long as they don't have a starburst or energy conserving logo.
>>> Bob Helt
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