As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING A ROUTINE COMPRESSION CHECK, EXCESSIVE LEAKAGE PAST THE PISTON RINGS WAS FOUND ON THE THE NR 2 CYLINDER. THE REMOVED CLYINDER WAS FOUND WORN OUT AND THE PISTON RINGS STUCK IN THE RING GROOVES. SUBMITTER SUGGESTED POSSIBLE CAUSE AS EXCESSIVE LEAD SLUDGE BUILD-UP FROM THE USE OF TCM APPROVED MOBIL AV1 OIL.