Polymerizing is merely the substance chemically changing due to any number of factors. All you have to do to polymerize castor oil is to heat it to about 400F for a number of hours. This changes the chemistry of the oil so it will mix with other solvents - like gasoline. In the case of castor varnish - the varnish will form at temperatures below the smoke point, but many don't realize that the varnish continues to lubricate. This varnish is what keeps ferrous technology engines "alive" for so long. (Ferrous technology engines employ a Meehanite piston in a hardened steel cylinder liner with minimal taper) The varnish provides some of the piston sealing. I don't see much varnish formation in car engines, but definitely see it in aircraft engines - mainly due to the higher operating temperatures and extended high throttle usage.

Benol will mix with some or most glow fuels, but I've seen pictures of people adding Benol to O'Donnell's fuel and it acted like oil and water - not miscible in that particular fuel. Why - I'm unsure. I don't leave anything to chance - I won't use Benol. I'll almost guarantee virgin castor would mix though. Castor oil has been the oil of choice for decades and there are thousands of engines operating today that were new 30 years ago that still perform as well today as they did back then because of the castor oil. In many of my engines, I use a full castor diet free of any synthetic oil - including 4-stroke cycle engines. They run well on it and carbon is rarely an issue.