<VV>High Mileage Oil for our engines

Bill Elliott corvair at fnader.com
Sat Dec 8 22:06:29 EST 2007

More detail:

*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.
> Bill
> 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 
>>> (ZDDP)..just
>>> as long as they don't have a starburst or energy conserving logo.
>>> Regards,
>>> Bob Helt

More information about the VirtualVairs mailing list