The contact owns a 2013 Hyundai Sonata. The contact stated that over time the vehicle became slow to start and that the engine was rattling and shaking abnormally at start-up. The contact stated while driving at undisclosed speeds, the check engine warning light remained illuminated. The vehicle was taken to an independent mechanic where the vehicle was diagnosed and the contact was informed that there was oil inside cylinder #1, causing a loss of compression. The contact was informed that the engine needed to be replaced. The vehicle was not repaired. The contact related the failure to NHTSA Campaign Number: 17V226000 (ENGINE AND ENGINE COOLING); however, the VIN was not included. The manufacturer was not notified of the failure. The approximate failure mileage was 125,000.