Could also be water and steam. When I worked at the Huckleberry RR, we used a 55 gallon plastic drum filled with water and a strong industrial detergent (I think it was called Clean Cargo). To the drum was mounted an old beater injector and we ran a steam line to the shop boiler and the output was connected to a long steam hose with a wand and a nozzle. Usually worked well for cleaning most anything that could stand the heat of the steam & hot water. The injector water supply was typically choked to the point of having both water and steam coming out of the tip of the wand.

The steam+detergent or steam+kerosene methods work great, but the oily effluent must be safely disposed of. Dumping it into the ground, the standard method during the Age of Steam, is no longer acceptable or legal. A professionally designed system would have drip collection pans, an oil separator, permits, wastewater quality monitoring, etc.

For more limited budgets, first protect the ground with oil-only sorbent pads. "TrackMat" is a popular brand which is UV-stabilized for outdoor use. These capture oil and shed water. Attach TrackMat to the ties with broad-head roofing nails. Trackmat rolls are sold in two widths: 59" for between the rails, and 19" wide for the ties outside the rails. Total cost including shipping is about $7 per running foot for inside plus outside the rails. That sounds expensive until you consider the cost to remediate spilled oil and grease. I know of a 5-gallon spill on the track cost roughly $5000 to professionally remediate, with volunteers doing almost all of the actual digging! That $5000 would have bought over 700 feet of TrackMat, and would have saved lots of time and paperwork.

Another good idea is to first wipe as much as possible off with rags and diesel fuel, or rags with an orange-peel-based cleaner. Oil-soaked rags cost about $300 per 55-gallon drum to dispose of as "Oily Solid Waste". That's cheap compared to most any legal alternative. Avoid using more volatile solvents such as paint thinner (mineral spirits). Disposal costs increase dramatically if volatile-solvent-soaked rags are mixed with greasy diesel-fuel-soaked rags. Disposal costs go absolutely beserk if chlorinated solvents such as "Carburetor Cleaner" are mixed in with the oily rags. Beware.

I recommend buying 100%-cotton rags because they absorb better than poly-cotton blends. Good all-cotton wiping rags cost about $1 per pound from your local rag company. We buy "Turks" ("Turkish towels"), which are cleaned recycled hotel towels that have been cut into smaller pieces.

- Doug Debs
Hazmat Manager, Niles Canyon Railway

One is Steam the other is cold water which will become hot when the steam mixes with it.
Simple green as Don mentioned is wonderful for all cleaning and it is biodegradable so the greenies can't get you. Power washing the running gear is easy just don't use the high pressure near the driver pins/bearings, hand wash those areas. Don is correct again that a little oil on a rag will make the engine look great but it becomes a giant dust magnet. Wash and wipe your engine, that is all she needs. One last thing, power washing drives water through every small opening in the jacket wetting the insulation and starts rusting the boiler shell. Better to hand wash the entire boiler and power wash the running gear and tender.