Thanks a lot for your informative replies downunder, mikeL, horace.

I did learn from it, yes, nitromethane is a hydrocarbon, and is used as fuel additive but I read its also called rocket propellent, as methanol is concerned which is ethyl alcohol its the real thing alongwith castor oil or synthetic oil. Related to it, though it seems to be little different question, but I wanna ask, when we talk about 2 stroke engine, it is cheap in price, gives more RPM than a 4 stroke. But when it comes to 4 stroke engine, it is said, the it sounds realistic, which it really does, also its expensive why its expensive Im still unable to figure it out, third thing its fuel efficient. Fuel efficient in what way? does it consume less fuel and give more flying time than 2 stroke engines? cos it completes it cycle in 2 stroke, where a complete combustion cycle in 2 stroke engine takes 1 stroke. I also heard that maintenance of 4 stroke engine is really difficult and once 4 stroke engine starts bothering you, its really pretty difficult to set them according to your desire, how much is it true.

Thanks in advance again

Mody