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. Kerosene ignites at 100 degrees F (38 C). Mineral oil ignites at a much safer 335 degrees F (168 C). Either of them is fine in an oil lamp. But kerosene’s burning point is too low to safely use in a model train.
How smoke units work
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. Mineral oil needs to be heated to 225-300 degrees F to vaporize. That’s a few degrees lower than required to ignite it. But that’s above the temperature required to make kerosene burn.
So kerosene isn’t what you want for the smoke unit. Neither is WD-40, which is an oil blend that includes kerosene. I’ve heard of people using that too.
The old-school Lionel smoke pellets, the kind you can’t get anymore, work similarly. But mineral oil is much cheaper, so that’s the direction the industry ultimately went.
Why so many people look for smoke fluid substitutes
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, or the pharmacy section of your favorite discount store, 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 your favorite lamp oil, but it will smoke, and it won’t set your train on fire either. And mineral oil is not expensive. You can get a 16 ounce bottle for as little as $2.
I’ve also heard the suggestion to use baby oil. Baby oil is mineral oil and fragrance, so that’s OK to use. You can even get it in lavender scent, which reminds me of the story of why I’m not allowed to buy laundry detergent anymore.