One reason not to use motor oil as bar lube

[scotclayshooter]

Most cars have a magnet on the end of the plug to get all the metal crud out of the oil anyways.

And some in the filters as well. I was changing Kubota filters the other day that had magnetic rings in the filter
But the magnets are not going to work with the metal in crank bearings
Like i said i wouldnt use used oil in my saws
there must be some nasties in new bar oil as well?