tommayer wrote:

Paul,
    A/C engines run on Mobil 1 would develop gray sludge.  It appeared to
affect the guides on Lycomings--I had trouble with that on an O-320, great
compression, great cold weather starting, but consumption went up quite
dramatically after about 600 hours of Mobil 1--and I remember reading that
there was concern about it clogging galleys on Conts.  The engine builders I
know thought the full synthetic was unable to scavange the lead in even LL
100.  I was never sure it was that simple, because I had run the O-320 about
75% of the time on no lead car gas.The engines run on the stuff were very
clean and low wear at tearn down, except for the sludge.

     I believe Shell engineering was a little more sophisticated, discovered
the problem in testing full synthetics and for that reason went to a semi
synthetic for A/C engines.  If turbine oil is full synthetic, and if you
have to buy much gas at airports, perhaps you ought to be leery of
encountering the sludge problem with turbine oil.

    You could probably avoid the drain off problem, if it exists, by using
Lenkite or Lycoming LW-16702.  The new Exxon semi-syn multi grade, Aeroshell
multi grade and Aeroshell W oils are supposed to have sufficient LW-16702,
or the equivalent, in them to start with.   Tom Mayer

 
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