NHTSA Complaint #11669595 — 2018 HYUNDAI SONATA

I purchased this vehicle from the seller the vehicle then immediately gave me engine issues. I contacted the Hyundai dealership which the vehicle got recent services with. They told me that the claim was denied even though the car has an extended warranty until 120,000 miles and the vehicle has less than that due to a regular oil changes they recommended me call Hyundai corporate to see if they can help out. I then contacted Hyundai corporate, and they essentially stated the same thing saying that the vehicle did not qualify for the extended warranty due to outside factors which were the irregular oil changes. I let them know that the vehicle did not get regular oil changes and I provided them with a Carfax report they then told me that in order for the card to be classified as getting regular oil changes and maintenance is every 5000 miles and this vehicle got most of his oil changes done 10,000 and 15,000 miles now I am stuck with a vehicle with a engine that is knocking even though it should still be under warranty