I've had over 100 new cars, so none have been very old. Of course, I worked for Ford Motor Company, and most were company cars.
Now that I'm paying, my oldest is a 2003 F250 diesel that has very low miles. At this rate, the engine's going to be worn out when I'm 97 years old.
The modern cars are built with much tighter engines, and they can still be reliable up to 200K miles. Of course the brand matters too. A Honda and Toyota will last longer than a 4 cylinder GM, Chrysler or Mitsubishi product.