As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: AN EMERGENCY WAS DECLARED AND THE AIRCRAFT RETURNED TO ORD DUE TO THE FLIGHT CREW REPORTING THAT ON TAKEOFF LOW OIL QUANTITY INDICATION. OIL ON NUMBER 1 ENGINE WENT TO 1.5 QUARTS AND OIL PRESSURE REMAINED SOLID AT 40 PSI. THE FLIGHT CREW REPORTED THAT THE ENGINE WAS NOT SHUT DOWN. THE AIRCRAFT LANDED SAFELY AT ORD AND TAXIED TO THE GATE UNDER ITS OWN POWER. MAINTENANCE NOTED OIL IN THE HPC DURING THE ACCOMPLISHEMENT OF A BORESCOPE INSPECTION OF #1 ENGINE. MAINTENANCE REPLACED THE ENGINE PER TASK CARD 26L40071001.