Because of the speed of development of new engine oil standards and related chemical developments the formula changes all the time. If you change your oil once a year, there is a high likely hood you have had a different formula in each change. This is good, you want supplier that is taking advantage in the latest lubrication improvmnts. This is why I am no longer brand loyal. Much of the time I use supertech now. Besides I drive old beaters, so the latest does not apply to my engine, which mostly always outlast the car anyway.