Depends on the vehicle, how broken-in, how driven, how maintained. So there is NO one answer fits all. I am a daily driver, buys new, follows the maintance manual and easy driver. I think Cars I buy like Mazda CX5, Subarus, Older Saabs etc are considered middle aged at ~ 80 to 100,000, old at 150,000 and old at anything over 175,000. High mileage is when you start having big dollar issues from the vehicle and not just for the engine in my opinion. Ed