Thimble Drome

what kind of fuel to use in cox 049 engine?

hi i have a cox .049 thimble drome engine on a control line airplane. i dont know what kind of fuel to use in it. can you help? i have a tank of some green fuel but i think it is 100% synthetic, i think, whatever synthetic means. thanks

Nitro =25% +
Oil = 20%
It will run on less Nitro but won’t develop max power and could be hard
starting. Brings back memories.

1950 Roy Cox Thimble Drome Champion Toy Car