The general rule of thumb is for conventional oil (most frequently found in older vehicles), you should change oil every 3000 miles, and for synthetic oil every 6000 miles. Best practice is to adhere to the maintenance schedule in your owners manual and change oil by the mileage or time interval specified. Some manufacturers have begun to claim that oil life can be stretched to 10,000 miles, however, if the oil has not broken down, become saturated with contaminants, or lost viscosity, you are still circulating through the same dirty oil filter without an oil change. Oil life is dependent upon each individual’s driving conditions. When compared with the cost of an engine repair due to poor lubrication, regular oil changes are an inexpensive maintenance, necessity.