ORIGINAL: Dwayne
According to the Bryon web site they use either 18% or 20% total oil content, this is pretty common and all you need to do is add 12 oz. of castor to a gallon of fuel this will bump your total oil content up to around 25% to 27% depending on what fuel you're using and you will be good to go.
This is where I get my castor.
http://brodak.com/castor-oil-quart.html
Good luck
Dwayne
It doesn't work that way. When you dump more oil in the fuel you decrease the alcohol and nitro content (all other additives as well), so those have to increaseby the same amount to keep the same ratio in the mix.
JK