Castor oil is superb in high temperature applications but has one nasty habit - its molecular structure changes after being heated and it congeals to an unpumpable, undrainable gell at cooldown. If it's allowed to cool to ambient temperature in the device, that device has to be disassembled and the goop literally dug out. Castor oil was used for WW-I aircraft engines as well as early race cars. In addition to prompt engine drains for those pilots fortunate enough to make it back from a mission, the lack of valve covers meant the pilots were constantly exposed to castor oil mist. Those brightly colored scarves the pilots wore weren't merely for jaunty show - they protected the pilots' mouths and nostrils from excessive exposure to the oil mist. Even at that, the pilots still ended up with strong urges by the time they landed. Latrines were thoughtfully provided near the end of the taxiways for those really regular guys. In that era there were old pilots and there were bold pilots. There were no constipated pilots, though.