I got a good deal on a Craftsman air compressor - belt drive 4 hp/20 gallon tank for $100 (including about 75 ft of good air hose.) I need to change the oil and the sticker on the tank says to use 20w20 non detergent oil. All I can find is NOS on ebay, and it's expensive! I am wondering if oil marked "air compressor oil" would be a good substitute? I can't find any weight ratings on air compressor oil. Does anyone know the difference between the oils? Anyone with this type of older belt drive Craftsman compressor, what have you used for oil changes? Thanks
