ORIGINAL: Gray Beard
I notice airtime mentioned synthetic fuel, that's not a bad way to go. I have tried it, not the green though and it is a much cleaner fuel. The bulk of the snot is the Castor oil. My number one brand fuel has always been Power Master 15/18. The 18% oil is fine but being a blended fuel there is still a lot of nasty snot blowing out. When I could no longer get Power Master I went with Wild Cat 15/16, much cleaner but 16% oil gave me pause so I added in two ounces of Klotz oil, that brought back the snot factor though. I'm now able to get the Power Master 15/18 again so I will be leaving my Klotz for my gas engines. If it's just the clean up that's the problem then buy a jug of full synthetic and give that a try. By placing my engines on there side or inverted I'm able to deflect the snot away and have very little clean up. I have one plane with an upright engine and it's a total mess after one flight, even with the deflector. There is just no good place to deflect the exhaust.
It HAS to be the GREEN kind if you're going to try this fuel. I've tried the pink(which also says full synthetic) and it was so bad I only made it through about a third of a gallon before giving it away!
It had the engines running hotter, was horrible during tuning, had several deadsticks and the worst was I started getting the brown gunk on the outside of my engines. Went straight to the LHS and grabbed two more gallons of green and haven't ever tried anything else.