I know this has been discussed several times, but I'm still not clear on a few things. Are you supposed to run an air dryer/filter unit on your air compressor if you are using these pumps? Or, are you supposed to use a regulator/filter combo unit right before the pump? If you look at most new low pressure systems that are for sale they have one of these installed on them. I currently have none of the above installed at my car wash. When I do some repairs on my system I notice that the air line has some oil in it. It would be nice if somebody from flojet could answer this question. I have had mixed results with these pumps, but overall I like the size and easy change-over aspect and for the most part reliability has been good. I can't help but think an airdryer/filter would give me better longevity.