Pure castor oil, yes. Degummed castor oil doesn't break down the same way as it heats up. Pure castor oil breaks down into even better lubricants, only losing its lubricating ability when it finally breaks down all the way to varnish. I wonder if Runner Time fuel has pure castor oil in its lubricant package. I know I saw a big improvement just from adding 1% pure castor to my Byron's 30%/11% fuel, which advertises that it contains degummed castor oil.