One thing I forgot to mention concerning UMO. When I was growing up, we didn't have a lot of money and my Dad took UMO, filtered it, and then used it again, sometimes adding a percentage of new high viscosity oil to bring the viscosity back up. He filtered it slowly, letting it drip through an automobile oil filter with no pressure. It took weeks to filter enough to use. I once took a sample of the UMO, after filtration, and looked at it through a semi-toy microscope I had. I remember seeing shiny metal particles in the oil, obviously very small.
I have never burned UMO in my Deuce and every time I hear about this practice, I remember seeing those small metal particles. I wonder how much wear these particles cause on injectors and the IP?