If you use castor based oil it will gum up your regulator, and if you use less than 20% synthetic, you run the risk of overheating it and voiding your warranty. YS says very clearly to use 20% or better synthetic oil only, and recommends 20% or more nitro. If you go with 30% nitro, you might want to up the oil to 23% or so because of the extra heat that will be produced.