As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PARKED AT GATE WE STARTED SMELLING A HOT OIL ODOR THROUGH THE VENTS WITH APU RUNNING ONLY. C/W WORK CARD ODI. REPLACED RECIRCULATION FILTERS PER WORK CARD 0550-2003. NO ODORS/ DEFECTS NOTED. NO GO ODI PREVENTION ATA 2172 C/W. RAN APU WITH PACKS FULL HOT FOR 2 HOURS. (LP# 4578950)