The contact owns a 2017 GMC Terrain. The contact stated while driving at an undisclosed speed, the contact discovered that there was an oil leak. No warning light was illuminated. The vehicle was taken back to the residence and the contact self-diagnosed the vehicle and was able to confirm that there was an oil leak, and the oil leak was coming from the rear main seal. A dealer was not contacted. The vehicle was repaired; however, the failure persisted. The manufacturer was notified of the failure. The failure mileage was approximately 115,000.