After doing some research, apparently 2011 was the first year of Hyundai's new Theda direct injection gas engine. Now, after a few years they are becoming known as sludgers, prone to sudden and catastrophic engine failure/seizure. Hyundai is apparently denying as many warrantee claims as possible citing sludge due to improper maintenance, if the owner cannot prove that all oil changes were done and the proper oil and filters were used for each one. Looks like a big problem for owners.