High School Volunteer Needs a Hand

Good morning, I am a parent/volunteer at my son's high school. Their competitive air rifle team uses SCUBA tanks to charge their rifles. Until recently, they used a Crosman recharge pump similar to the Benjamin recharge pump, models CHPAC/BHPAC respectively to charge the tanks. From what I understand, the unit is not compressing over 500 psi, which is way under its 4,500 psi rating. I took it home, serviced it with new 5w-40 oil and new distilled water, and checked the pressure chamber filter for trash/moisture, and it was all good. I also checked the blowout disc and release pins, which look fine and/or were secure. The observation that leads me to believe the piston ring(s) are shot is the oil smell in the output air and the air escaping from the pump vent pipe, which is venting a lot of atomized oil as well.

For those of you who are familiar with this unit, can you please give me your thoughts? Also, if anyone has this unit, can you please run your compressor and tell me how much air you feel coming from the two bleeder holes on either side of the vent pipe? I am unfamiliar with this sport and machine, and am only applying mechanical knowledge as I try to help the team.

Thank you.
 
I'm not familiar with the compressors you have but I can tell you that you are not close to the proper oil! But likely that is not the cause of low pressure.
Royal purple compressor oil is your best chance and cheapest to find locally.
Ideally you want breathable air compressor oil. Do a search for what compressor oil should I use.
 
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I'm not familiar with the compressors you have but I can tell you that you are not close to the proper oil! But likely that is not the cause of low pressure.
Royal purple compressor oil is your best chance and cheapest to find locally.
Ideally you want breathable air compressor oil. Do a search for what compressor oil should I use.
Thank you for the input. That's what I was thinking, but when I researched the oil spec, the manual calls for a 5w-40.