What are nitro powered RC cars? Are they gas powered or fuel powered? Wikipedia and rc website gave diff ans!?

MOST RC cars are either electric (EP) or nitro. I don't know of ANY models big enough to use 'regular' gasoline engines, (although there are model planes big enough); and, many people refer to the 'nitro' fuel as gas.

Nitro fuel is actually alcohol, with a percentage of nitromethane added (from 0% to 30%); and 10 to 18% lubricating oil of various kinds.
The amount of nitromethane and lubricating oil various with different 'blends' of fuel, AND the use for which the fuel is made.
A higher percentage of 'nitro' will produce more power, but will also cause the engine to wear out sooner.

Hope this helps.
References :
40+ years flying model airplanes.

Almost all internal combustion glow plug ignition hobby engines use methanol with varying percentages of nitromethane. Synthetic castor oil is mixed in for lubrication. The more nitromethane the more expensive and powerful the fuel is. Gasoline powered model engines are usually much larger and have spark plug ignition systems and look like chainsaw or weed-eater engines. The gasoline is mixed with oil for lubrication. So you can almost always tell what fuel is used by the ignition system.
L&N nut
References :
personal experience