RE: Cox Super Power 1/2A Fuel 25% Nitro Quart
While castor is the preferred oil for 1/2A especially Cox a little synthetic is not a bad thing to have in the fuel. It is really helpful in preventing the formation of varnish on the cylinders which they are all subject to getting. Also keep a Davis de varnishing brush to keep the bore clean.It's amazing how bad these engines run with varnish and how difficult they are to start until the varnish has heated and liquefied
Dennis