Home › Forums › Stay Dirty Lounge › Service and Repair Questions Answered Here › Elantra 2012 1.8L "NU" engine tap/knock › Reply To: Elantra 2012 1.8L "NU" engine tap/knock February 12, 2020 at 10:26 am #897239 Richard KirshyParticipant Might suggest trying Marvel Mystery Oil added to the crank case according to the directions and see if that helps.