Standard machine oils plainly
have a limit of 180*F, whether it is ship or motor. They can take more abuse for a short time, however breakdown is ongoing once the limit (however defined) is reached.
Organic oils: Once separation occurs, that’s it – jig is up; break down begins and it cannot be reversed. Hydrogenated Paraffin looks like pudding or yoghurt; white mushy mass, waste of good materiel, frustrating to clean. Measured in buckets
on modest ships at sea. Damaged oil is required to be replaced; there is no alternative, even with filtration; that only removes more paraffin.
Synthetics have much higher heat tolerance; they are less affected by natural agents that cause lubrication failure. Think Amsoil!
A long career studying lubrication awaits the capricious few; kingly is the sire that solves the elusive problems of heat transfer and fluid flow (no pun intended). The problem is ginormous: Isn’t it amazing that all society hinges on the effectiveness of a thin-film long-carbon chains at the boundary layer under punishable conditions is really all that keeps our world afloat? (a bankable pun)
FWIW, Amsoil was one of my clients in ’92, as was Standard Oil in ’98. The technology surrounding them, aside from being a most-eye-opening technical culture, is amazing! I didn’t say they were Scott-free on the environment, no! Just appreciative of the science and industry.