Manufacturers of automobiles have chosen to use many long-life auto parts and fluids to cut back on the maintenance costs of their vehicles. The manufacturers of these 'long-life' products make many claims about how long they last. For example Nissan uses an anti-freeze that the manufacturers say lasts ten years or 120,000 miles. However, Nissan recommends that car owners change it every four years or 60,000 miles. Why the difference???