I have been using OMEGA for a few years now. I like the Castor/Synthetic mix myself. All castor gums up the engines, but a mix seems fine and clean using this OMEGA 10% Nitro. I have tried 12.5% and 15% but did not see any benefits from it, except a much higher cost. Castor can be purchased in a plastic bottle, and I prefer to add a little to the fuel as an extra measure when breaking an engine in, my personal preference and I kind of like the smell when the engine is racing in a low fly-by. There are fuels this one hobby shop I buy fuel for $14 per gallon by the case way out near Vernon, NY and it is the OMEGA. Flying field across the road is a plus. This is where I got the small bottle of a few ounces of Castor Oil from and is for those wanting to mix their own fuels. So, it is hobby approved.