Yes, it is - nasty stuff. I get it off of stainless and brass with denatured alcohol or acetone on q-tips or acid brushes. Don't let either of those get near painted surfaces, though.
It does do a good job of getting that hardened amber looking stuff off of bare metal - you can see bits of it left on the top of this fitting on the bottom. I think that's considered a sure sign of someone using 3-in-1 oil.
Funny thing is, 3-in-1 oil used to be advertised specifically for sewing machines. :)
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Don't - believe - anything - you - read - in - this - ad! ;)
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