MD-82
Time Pressure; Distraction
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Maintenance
General None Reported / Taken
Human Factors; Staffing
Earlier in the evening one of the mechanics was slightly injured on another aircraft and was in the office.  Since he was part of the crew; and I was assigned the oils I thought I would help out by finishing quickly then going up to do part of the interior check. After cleaning the APU; I checked the oil quantity and noticed it was down a pint. After servicing it I was placing the cap back on when the oil bowser fell from the lift and started to leak oil. I quickly picked up the bowser and cleaned the area. I ran the APU then closed the door [but] did not verify if the cap was fully closed. This happened at gate shortly after midnight. No other mechanic was involved.
A Maintenance Technician neglected to ensure that the oil cap was securely repositioned on the APU oil tank after servicing.