I would run at least 5% castor in my fuel for most engines. You can get AA castor or Klotz Benol or other racing castor and add it to your fuel. Some folks still don't get it, but when you get a lean run, and you probably will from time to time or in high temp, the castor will form high temp polymers and protect your engine quite well. A lot of fuels are a bit low on total oil, or the oil is not very good in the first place. Also, you can run 10% nitro, which is plenty for many applications, 15% better for my Saito FA091S engines, but in 4-strokes, if you use castor, use under 4% and just 2% is about best. I know a lot of folks run all synthetic, but if you run green snot at about 17% oil, you will enjoy your engine less time that you had hoped. You have a nice, powerful engine. If it were mine, there would be some good castor in there as well as synthetic oil. These comments refer to NON-ringed engines. Non-ringed engines still benefit from castor and with proper maintenance is no problem for these engines. Putting 17% oil green fuel in nice ABC, AAC and AAN type engines is not really a good idea in my experience, despite the "slightly rich" runs claimed by a number of modelers for this 17% fuel( probably true), but a lot of modelers do not run their engines rich with this type of fuel. In a hot flying day or lean run, there is a good price to pay with these engines. The old fuel mixing dinosaur.