liquid smoke substitute???? - Model Railroader Magazine

Smoke fluid is really just mineral oil, but it's mineral oil of a specific molecular weight(boiling point), and perhaps more importantly of a specific viscosity.

There are two general types of smoke units in use-the wick type, used on most Lionel and other large engines, and the seuthe type, which is far more common in smaller scale engines. 

The wick type units aren't really picky about what type of fluid they use, although oils which are too viscous can clog the wick, and leave behind a high-boiling residue that can cause problems. 

Seuthe units, by contrast, draw the smoke fluid up a narrow glass tube by capilary action. Because of this, viscous fluids will easily clog the capillary, and ruin the unit. 

Seuthe units really should use Seuthe smoke fluid. Wick type units can use seuthe fluid, but it doesn't give the best results. 

Some have had good luck using lamp oil in their wick units, but I personally would shy away from this because lamp oil is really designed to burn and not vaporize, and may work as designed at a most inconvenient time. 

Under no circumstances should commonly available "mineral oil" or baby oil be used in either type of smoke unit. It's far too viscous, and probably will cause problems.