It seems then that yourself and your friend know more about the compressors than the manufacturer. Some people also smoke heavily everyday and still live to be over 100 years old. That doesn't mean that it's OK to smoke. The fact that you cannot see the contamination in the line doesn't mean it's not there. This is a known fact in pneumatics. I guess than there isn't more to discuss about compressors since all of the questions have been answered.