I have an old air compressor in my garage at home mostly used to fill up tires and sometimes for my air tools i use at home every now and then. It was bought by my dad in the early 80's and the oil was never changed i think it requires 20w non detergent but i am not sure anyone have any ideas it is an old sears with an electric motor. I want to change the oil on it because sometimes i use the impact tools to do brakes (taking wheels off) because we are always cramped at the shop with cars everywhere.