I have a 2014 M5, bought in 2016 off lease with 36,000 miles. Dealer CPO'ed it and bought extended warranty. Have 53,000 miles on it. Drove 175 miles round trip Wednesday, no problem. Thanksgiving morning, crazy knocking sound, brought it to dealership on Friday and told internal engine failure, engine and turbochargers need to be replaced. WTF? Fix is $46,000, warranty only covers $40,000 (NADA value of car), if they cover it at all. Dealer is tearing it apart in response to warranty company's many requests for more information. So far, no explanation for failure, except that bearing may have gotten stuck and snapped connecting rod, whatever that means. Car properly maintained. Any ideas, thoughts, suggestions, information about anything happening, or possibility of BMW stepping in?