My take on it is, lower flash point oils get lit up sooner,
this gives them more tiem to burn clean, leaving no ash but probably
a hotter saw which also helps a cat to do its work, but that kind of heat
is not what I like.
The good synthetic oils have higher flash points, and that because syntheic
oil can work at higher tempratures, this results in these oils not getting lit
up in time, thus they spend a little more time oiling before they are spat out,
not as cleany for the very high flashpoint ones, and that is the compromise.