I think I have tried all kinds of oil. One of the worst machines I worked on was an old Singer 401G. I used 3-in-1 oil on it. Initially it worked. Then it set for a few weeks. The machine acted like it was encased in concrete. I think I tried everything to get the 3-in-1 oil off. Maybe it was a combination of the 3-in-1 oil and the dried up SM oil. I believe I tried kerosene with some success but I wasn't happy with the results. I heard of Tri-flow and Kroil but I couldn't find it locally. I had a couple really stuck machines and used kerosene or brake cleaner or xylenol to get the old gunk off, then re-oiled with SM oil. It was a lot of work. Then I found T-F at sew-classic. I had a machine that was pretty much frozen up.
http://www.quiltingboard.com/vintage...r-t169127.html In a matter of minutes we had it unfrozen. I experimented with the T-F after that. I used it on the 401G and let it set for about a year. At first it was a little stuck but then it was right back to where it should be. I'm thinking the teflon is just like the stuff on your cook ware - I won't use it for that because it doesn't stick to the metal. I don't see any long term setting up from the T-F but I do from stuff like 3-in-1 oil and SM oil - lots of paraffin in it. I think it is the machines setting around that freezes them up. Use the machines. Turn them once in a while. You can always oil a machine with SM oil and another with T-F and see what you like best. For me, I'm liking the ease that they turn when the T-F is used. PS I agree with Joe.