After spending quite a lot of time researching fuels I ended up ordering a couple different ones from Sig last Monday. I found (especially in higher nitro content) other fuel brands with 20% or more oil advertising castor/ synthetic blends did in fact only contain 1% castor. Sig is the only brand I could find that clearly stated the mix percentages, and how much of the advertised oil content is castor. They were also the only company that gave the brand name of their synthetic (Klotz). I bought 10% nitro 20% oil 50/50 Klotz/ castor for the majority of my engines and 35% sharing the other specs for my 1/2 A engines.