My dear old dad laughed when I showed him a brand new $10 bottle of super duper gun oil. He claimed a good quality engine oil was every bit as good as any premium gun oil and explained why (pressures, temperatures, RPM, and duration between oil changes in an automotive engine). As he had been a chemical engineer, , tanker (1935-1938, 1939-1944) and firearms instructor (1944-45) I trusted him. I've used synthetic motor oil on guns (and motorcycles and cars) for over twenty years now and it works great! Where applicable use grease but everywheres else use synthetic motor oil. One guy in the club is an instrument mechanic and he also uses synthetic motor oil. It works great!