The manual always says 7k for oil changes no matter what the oil is.But there is usually an * that says under extreme conditions change at 3k.Extreme conditions are considered stop and go driving and short trips.The goverment makes them put the 7 k intervals.The manifacturers are getting tougher on engine repairs and will ask for oil change reciepts. I've had customers spend 5 grand on a motor and still not change their oil.I pull out the drain plug and sludge comes out.If you want to be cheap go ahead.I will change my synthetic at 3 to 5k.Also mercedes had lawsuits because there dealers were putting in regular oil and the customers were following the syn. maint. schedule and damaged their engines.