Mopar, funny you should say about actual miles of testing. While I havent see it advertised much lately some manufacturers seem to actually run the miles to get the results.

Remember back in the 60s it was a big thing the torture test the cars? They'd run like 4 Comets 100,000 at 100MPH around and around an oval. They'd test plugs, tires and all sorts of componments that way. I'd reckon they still do actual testing but I wonder if it's as much as it used to be?