Re: How to use castor oil??
I would use 20% castor/80% synthetic if you use 32:1 to 50:1 oil ratios.
If you are running 16:1 to 32:1 oil ratios, then I would max out at 10% castor/90% synthetic.
I'm a model airplaner too and know that it only takes a little bit of castor to fortify synthetic oil.