Lamp oil is basically kerosene. It has a flash point between 100 and 150F. The flash point is the lowest temperature at which a volatile vapor will ignite. Smoke fluid is, primarily mineral oil, which has a flash point around 335F. This is why you see vapor (smoke) long before you would see any any flame.
To paraphrase Jon, unless your objective is a Gomez Adams layout holocaust, stay far away from flammable liquids. Stick with smoke fluid designed for trains.