Bob's Synthetics Post

["Al Powell" <APOWELL@agcom.tamu.edu>]

Ovbiously, Bob Cohen was MEANT to be part of this group - after all, 
he's a "Bob"!!  (Bob, if you don't get this - it's a tradition on 
this list...welcome.)

Relative to your post, would you share with us your opinion on the 
following subjects:

1)  Ability of the four classes of synthetic base stocks to reduce 
volatilization under the heat and stress of engine use - COMPARED to 
whatever "typical" petroleum oil you care to cite?
2)  Ability of the synthetic base stocks to maintain engineered 
characteristics of flow and lubrication under extended (10K+) 
service?
3)  Ability of synthetic base stocks to resist breakdown under 
unusual heat,  such as an overheated engine, as COMPARED to petroleum 
oils?

> 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


*** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***

Al Powell                           Voice:  409/845-2807
Ag Communications                   Fax:    409/862-1202
107 Reed McDonald Bldg.             Email:  a-powell1@tamu.edu 
College Station, TX  77843-2112
W3 page - http://agcomwww.tamu.edu/agcom/rpe/alpage.htm

                    ***The PACK is back!***
*** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***