I was talking with the vibration guru (Doug) from work during lunch today and asked him what kind of oil he uses at home and the change frequency. He stated that he uses Mobil 1 in both his vehicles (Hondas - one with a six and one with a four cyl) and his change frequency for the oil and filters is the same as the Mobil Lubrication engineer that he deals with - twice a year - once in the spring and once in the fall. I was pretty surprised because in the lubrication engineers case you are talking over 15k miles between oil changes. Doug went on to say that the last car the Mobil guy had the engine lasted for over 300k miles with the majority of these being highway miles. If anyone is interested in discussing this with the Mobil lubrication engineer I can send his email address upon request. I change my oil more frequently than twice a year but then again I do not use synthethic oil.