If you read the fine print that's "oil service" every 12k, they still recomend a change inbetween "oil services". Oil loses its' detergents in roughly 3k miles (for non-synthets) and 6k miles (for syns). It still lubricates, but it loses its' cleaning abilities at roughly those mileage points. Read your owners manual or contact your dealers' service dept. for clarification.