Amsoil is a multi-level marketing company, with a variety of high end synthetic oils, synthetic greases, and many other additives, filters, and other car care products. One has to weigh the cost/benefits of the products against the benefits of extended oil change intervals, the benefits of low and high temperature operating conditions, etc. Amsoil claims up to 35,000 mile-or one year OCIs "non-severe service" with some of the engine oils, and about half that mileage in "severe service" conditions. From a cost standpoint, anyone not using the long time/mileage OCIs would be better off with quality, but less expensive synthetic or petroleum products, and conforming to more traditional mfg. suggested change intervals. Amsoil has a corporate web site available for perusal.