From what I've read, I should use a straight weight non-detergent in the air compressor because detergent oil will foam when it comes in contact with moisture. So, won't synthetic oil foam too? My compressor has a sight glass for the oil, so I guess I could see if the oil foams. I drained the oil and it was thick and dark looking. Also, for the first time, the 30a 220v breaker was tripped, so I'm definately going to put thinner oil in it for the winter.
Is there a special oil for air compressors? If so, where can I get it? Is it muli-weight?