Engine began making knocking sound then car while in the highway was not able to accelerate. This slowdown put driver at risk for highway accident. Took car to dealership. They said the engine needed replaced then the next day said no Hyundai said it needed a sensor. This was a bandaid fix as it continued to go through oil faster than it could be changed this led to engine shake and knocking several months after the band aid fix. The car was not able to accelerate again. Again took it to Hyundai dealership said it need an oil test required us to do and pay for an oil change when we had just done one. Drive the 1000 miles brought it back failed the oil test said they need to do some sort of engine clean. Hyundai refused as the car doesnât have oil change records for the first three years. No record of oil change was recorded even though they were completed. It being five and six years ago we donât have receipts but believe these were part of the lease and completed at the dealership at no cost. Now Hyundai not even doing the rest of the oil test but say engine needs replaced however they will not cover the repair. We have all records after the car was purchased off the lease other car we own has full oil change records but since we are not able to locate and no one recorded they have denied the repair of a known issue with their engine. This engine issue needs a full investigation as they are trying to get away with not fixing THEIR known problem. This is a driving hazard