Every so often, the topic of lamp oil as a cheap substitute for smoke fluid in Lionel and Marx trains comes up.
The topic has been beaten to death on many closed message groups, but finding the answer isn’t always that easy. But, in short, it’s not a safe thing to do.
The problem is ambiguity. Lamp oil’s main ingredient is almost always listed as paraffin. Depending on where it was produced, could be one of two things. In some parts of the world, paraffin is mineral oil, which also happens to be the active ingredient in smoke fluid. But in some other parts of the world, paraffin is kerosene, which you don’t want to be putting into a toy train. Since there are no regulations about lamp oil in the United States, it’s impossible to know whether you’re getting harmless mineral oil or potentially dangerous kerosene when you buy lamp oil.
Smoke units work by boiling the oil, not burning it. Like a real steam engine, the “smoke” you see coming out of the stack is actually steam. So kerosene isn’t what you want for the smoke unit.
I’m sure part of the motivation is cost and part of it is availability. In many parts of the country there’s no longer any such thing as a local hobby shop.
If you need a cheap and readily available substitute for smoke fluid, there’s only one safe way to get one. Go to a pharmacy and buy a bottle of mineral oil. It’s not likely to work as well as commercial smoke fluid, and it may or may not work as well as lamp oil, but it won’t set your train on fire either.