I have a Chevron product spec sheet for cylinder oils that was published in late 1984.
They offered 4 grades, 460 which was uncompounded and had a flash point of 570 degrees F;
460X which was compounded and had a flash point of 555 degrees F;
680X which was compounded and had a flash point of 575 degrees F;
1000X which was compounded and had a flash point of 650 degrees F.
It went on to say that the compounded oils should never be used when exhaust steam is returned to the boiler,
a condition not seen on most smaller locomotives. Compounding was achieved by adding wetting agents to the
paraffin base oils.
I had not given this much thought until I worked for the GCR where 4960 sometimes saw Superheat temps
just getting to 700 degrees F.