i got a bottle of royal purple when i bought the pump over a year ago .. havent changed it yet . i should simply to get any factory gunk out, but compressor oil isnt critical to change, its not like vehical oil that gets contaminated with combustion and 'cut' with solvent like fuel ... just make sure its at the proper level .. that 'is' critical, and after that first change to get the manufacturing grime out id say its good for the life of the pump ...