Before I fire up my new OS .91, I need to add some more oil to my fuel. I have a new gallon of Powermaster 10% that contains 18% oil. Anyone know how much caster to add to up it to 23% oil content. It's been too long to try and remember how to do the math. I am assuming that everyone is using at least 23% oil per the OS instructions. I suppose I will break it in per the instructions with a 12x6 wooden prob cut down to 10". Sounds like a recipe for disaster to me spinning a hacked on wooden prop at 20K. What are you guys doing for break in?

Thanks,

Mark

Check the latest issue of Model Airplane News. It has a formula for calculating the amount of oil to add to reach a desired overall percentage. I would take a fly at remembering the formula - but I was never that good at doing that when I was in college so I will pass.

Dan

I would not use 10% fuel in the OS.91. Wildcat 5% jet-a is the best, but sometimes hard to find. PowerMaster makes a ducted fan blend with 5% nitro and 23% oil content that is a castor/synthetic mix. I have a gallon , but have not tried it yet.
Install the engine in your jet and run it a little rich for a half a tank or so and go fly it.