Synth Oil Info (was: OIL vs EARL)

[rsco@lubrizol.com (Robert S. Cohen)]

First some background and disclaimers

Lubrizol develops and manufactures lubricants, additives, and other
chemicals for industrial, aircraft, and automotive uses.  You likely have
chemicals either developed by, or manufactured by Lubrizol in your vehicle.

I am not a tribologist, chemist, or mechanical engineer, nor do I play one
on TV.

I do not speak for Lubrizol.

I am a systems analyst consulting for Lubrizol.

Enough of the disclaimers.  I hope the following information can help put a
lot of the information, misinformation, and anecdotal evidence surrounding
synthetics (on the QuattroList and elsewhere) in perspective.  I leave it
to the reader to draw their own conclusions regarding applicability, seal
longevity, and oil consumption.

I think there is enough information here to build a simple, moderately
accurate model (hey, I'm a systems analyst) that is consistent with
seemingly contradictory anecdotal evidence regarding synthetic oil posted
to the list.

At the risk of appearing pedantic, please notice that 'Synthetic Oil' is a
complex blend of chemicals, and not some single formulation. Each blend
will have different characteristics depending on the base stock and
additive packages. Also, pay particular attention to the information on
seal/elastomer behavior, and solvency.

The following information is taken (either directly or paraphrased) from a
book 'Ready Reference for Lubricant and Fuel Performance'  c 1993, the
Lubrizol Corp.

Any typos are my fault.

start excerpted information------

There are 4 main classes of synthetic base stock with automotive applications:
Olefin Oligomers (PAOs)
Dibasic Acid Esters
Polyol Esters
Alkylated Aromatics

All of these have viscosities in the range of the lighter HVI Neutral
Mineral Oils.  "Their viscosity indexes and flashpoints, however, are
higher, and their pour points are considerably lower.  This makes them
valuable blending components when compounding oils for extreme service at
both high and low temperatures.

"The main disadvantage of synthetics is that they are inherently more
expensive than mineral oils, and are in limited supply.  This limits their
use to specialty oils and greases that command premium prices.  Esters
suffer the further disadvantage of greater seal-swelling tendencies than
hydrocarbons; so, caution must be exercised in using them in applications
where they may contact elastomers designed for use with mineral oils.

"Polyalphaolefins are the most widely used synthetic lubricants in the U.S.
and Europe....
        PAOs have good thermal stability, but they require suitable
antioxidant additives to resist oxidation. The fluids also have a limited
ability to dissolve some additives and tend to shrink seals.  Both problems
can be overcome by adding a small amount of ester.

"Dibasic Acid Esters ....
        Advantages of diesters include good thermal stability and excellent
solvency. They are clean-running in that they tend to dissolve varnish and
sludge rather than leave deposits. In fact, diesters can remove deposits
formed by other lubricants.
        Proper additive selection is critical to prevent hydrolysis and
provide oxidative stability. In addition, chemically resistant seals are
recommended

"Polyol Esters....
        Seal-swell behavior is similar to that of diesters.

"Alkylated aromatics....
        The fluids have good low temperature properties and good additive
solubilty....Thermal stability is similar to that of PAO, and additives are
required to provide oxidative stability.

----end of excerpted information



Bob Russell wrote:
>recently while at my local audi dealer i mentioned i wanted to start using
>synthetic earl in my 80,000 mile old  200tq.
>
>one of the mechanics (not roland the audi tech) said if the car has been run
>with regular oil this long, it may develope leaks around seals like cam or
>other areas. you may also notice an increse in oil consumption .
>
>Iam putting the change on hold.
>
>this should cause some interesting disscussion.
>
>look forward to your thoughts  i am sure there will be many

_____________________________________________________________________________
Robert S. Cohen

NewMedia Inc., 503 E 200th Street, Cleveland OH  44119-1545
voice 216.481.7900  fax 216.481.1570

The Lubrizol Corp., 29400 Lakeland Blvd  MS 228, Wickliffe OH  44092
voice 216.943.1200 x 2012 fax 216.943.7215

Email: rsco@lubrizol.com   rsc2@po.cwru.edu   cohen@nmedia.com
____________________________________________________________________________