Sure, you CAN use chainsaw bar oil... and you can also use peanut butter to grease your wheels ("Dennis the Meanace" did on his wagon) and you can burn moonshine in your Lambourgini. The locomotive will run... for a while, anyway.
Friction wear ALWAYS occurs, but with the proper oil it occurs very slowly. Use the wrong oil (or no oil) and the wear is accelerated considerably, and can sometimes occur almost in an instant. Chainsaw bar oil will NOT be carried in the steam other than as big blobs which will not reach all of the "wear" points consistantly. A split second of metal to metal rubbing and a significant amount of wear can occur, which can ruin the machine. One minute it is running just fine and the next it can either seize or have a significant amount of leakage.
Remember, one of the best ways to REMOVE oil from surfaces is to STEAM CLEAN it! If the steam is not carrying oil in it, the steam will clean the cylinder walls and the valve surfaces down to bare metal very quickly. Steam Oil, PROPER Steam Oil, will emulsify with the steam and reach all the wear surfaces. Chainsaw Bar Oil will NOT do so.
Also, notice the admonition to "filter" the oil! How much filtering will remove whatever it is that the suggester is fearful of leaving in the oil. It used to be said that bar oil was the "dregs" of the oil manufacturig process, the stuff that was "left over" after getting the good stuff out to be sold for the best purposes. I don't think that is true anymore, but if someone is saying to "filter" it, then there must be something in that oil that is not good for wearing surfaces, even though it is designed to oil a chain rubbing on the blade of the chainsaw. Do you REALLY want to put something in the steam engine that needs to be filtered?
