<<Is the flash point the temperature at which the oil cokes up?>>

<<I was told by an A&P that the redline temps of 245 provides a safety
margin
of about 15-20 degrees before oil cokes. Any further comment on this?>>

As I understand it the flashpoint and coking are two different things.  The
flashpoint is the temperature at which an open flame above the liquid will
ignite the vapor, so it is a measure of how many "light ends" there are in
the oil - mostly looking for gasoline contamination.  The flashpoint will
gradually rise as the oil gets older because the more volatile components
will gradually evaporate during use.  Coking is the gradually oxidation, or
burning of the oil.  This accelerates dramatically as the oil goes over
maybe 275 or 300F.  Synthetic oil will have a higher coking temperature.

Gary Casey
ES