nitro rc car how do i know what fuel it takes please help?

its a small racing one not sure how big the engine is neither does the person who i bought it off. no box can i use dot 4 oil and petrol mix. or is there a universal fuel.

find a hobby shop around you, they can look at it and see what fuel u can use. no one will be able to figure it out on here cuz u have no info on the thing.