I have a Model 325 and I ordered a 1 gal. jug of Quin-Cip, (Quincy brand) oil when I rebuilt the compressor. That was over a year ago and I still haven't used it all since it mostly sees action only on weekends. Like others have said though, I'm sure any non-detergent oil of the correct viscosity will work.
I bought all my parts, including oil and filters, from Industrial Air Power. If you have the Quincy parts manual for your compressor just grab the part number and type it into their catalog. They sell both OE and aftermarket parts. Note: I have no affiliation with IAP, just found they had all the parts I needed at a decent price.
Catalog here:
Industrial Air Power