That was fascinating. Thanks for the link!

Btw, I suspect the real reason why castor oil was used as the benchmark in those old lubricant-comparison tests is because it's the only readily-available, inexpensive oil that dissolves easily in alcohol. Glow engines became popular in Europe after WW2; synthetic oils were in their infancy and terribly expensive, and petroleum wasn't readily-available again after the war had ended. But normal people *could* get their hands on methanol and vegetable oils, and of all the commonly-available vegetable oils, castor oil dissolves in alcohol the best. It's a happy coincidence that it also decomposes into *even better* lubricants when it overheats.