When you look at the surfaces of your pistons, valves and other engine parts, you’ll see how smooth they appear.  However, beneath a microscope, things called asperities are revealed. These ridges, hills and valleys in the metal are what help to sustain the lubricants as parts are moving inside your engine, transmission, bearings, and rear axles. However, when a lubricants fails – usually due to the additives contained within them – these microscopic metal surfaces begin to interface, creating friction followed by heat, and then metal failure, or the welding together of the surfaces.