A portable, rotary vane vacuum pump with a rotor eccentrically mounted within the bore of a housing to substantially abut the bore at a side location. The abutting, side location is between the inlet and outlet passages of the bore in the direction of rotor rotation. A pocket is then created just above the contact area between the rotor and bore which collects and maintains a pool of lubricating oil. The pool enhances the seal at the contact area below it enabling the pump to draw a deep vacuum with just a single stage. The portable pump also includes a removable, oil reservoir cartridge mounted to the main body of the pump. Other features include a visual indicator in the cartridge to monitor the condition of the circulating oil, a step up gearing arrangement for the cooling fan, and a step down gearing arrangement for the vane pump.