I have a Sears Craftsman Air Compressor that is 27 years old. It is a twin cylinder 6.9 SCFM at 45 PSI. It can run on 115V/220V. It ran the first 17 years on 220V and the last 10 on 115V. Oil has been changed at least 10 times in its life. Yesterday I changed the oil and added 16 ounces of oil plus 1 ounce of Auto-Rx. I ran the comperssor for over an hour on my gas generator. Nothing seemed to change except that as time went on the generator did not seem to lug as much when the compressor kicked in. (Subjective) Nothing else that I could tell. I will run this all summer and change the oil in the fall. This thing is like the energizer bunny, it just keeps going and going.
