The only thing in "Castrol" that is close to castor oil is first four letters of their name.
All of the oils they sell are either petroleum or synthetic oils that reproduce the best qualities of petroleum oil.
None of their products that I know of use any real castor oil.
Glow fuel, for those interested is a mixture of alcohol, nitro-methane and castor oil.
It ignites due to the heat of the small coil of glowing wire in the glo-plug.
The heat of the burning fuel reheats the wire so it can light the next fuel/air charge at the top of the compression stroke.
For those who are curious, there are also Diesel model engines which work off of compression alone.
These burn a mixture of kerosene, ether and castor oil. They can be identified by looking at the top of their cylinder head.
Rather than having a glo-plug, they have an adjustable screw (often with a cross pin to grasp)
which adjusts their compression.
The ether serves to ignite the kerosene and like the glo-plug engines the castor oil serves as the high temperature lubricant.
By the way. I have a lot of both types of these model engines. Their piston and cylinder are made from carbon steel and many of them haven't been started for years.
Even though they have just been sitting in various boxes, exposed to the air and humidity, the castor oil they used when they were last started has prevented even the slightest sign of rust from forming. :hmm: