In very cold weather, castor oil turns waxy (it literally becomes a solid), but it returns to the liquid state when things warm up. If you use castor as after-run oil & store it outside, then want to use the engine in winter, you may have difficulty turning it over. That same phenomenon makes the use of castor lubed fuel inadvisable in very cold weather, you lose part of the lubricant. Additionally, the waxy particles in the fuel can clog the NV, leaning out the engine & robbing it of more lubricant.

Great stuff in warmer weather though.