I have two military surplus Davey 15 diesel compressors I am planning to part out. They both run fine but one has oil in the 4th stage gauge which tells me I have oil in my air. A military compressor repair guy told me it is probably a bad 4th stage piston. The other runs fine but the moisture drain wasn't working, so I ran a manual drain off the water traps, but still got water in the oil, so now the air has a slight smell even after changing the oil and filters. I have decided to get rid of them rather than mess with them. I have a custom built trailer I had built for one that I am also getting rid of. I understand the filters are popular as a backup system. you can also call me at 701-667-1312 if you want to talk about it.