How often should I change the oil in my car?

The vehicle manufacturer specifies which grade of oil should be used for the vehicles it produces. The manufacturer also specifies how often the oil changes should be made. For example, most people in the United States believe that a common oil change frequency should be every 3000 miles or every 3 months, whichever comes sooner. This 3000 mile oil change interval has been relentlessly promoted by oil changing companies for decades. It had a scientific basis when engines used non-multi-weight, non-detergent oil. It no longer has any scientific basis, but it is still being promoted by certain entities, most notably the oil change industry in the United States (including car dealerships). Indeed, studies have shown more wear occurs with fresher (1000-2000 mile) oil. This is attributed to additives re-establishing themselves, TBN converging, and filters becoming more efficient. Most manufacturers recommend oil change intervals of 6,000 miles or more for modern cars. In Europe, by contrast, where the influence of oil companies has been much less, oil is typically changed only at a major service interval, between 10,000 and 15,000 miles for a modern car. For convenience, the oil filter is usually also replaced at the time the oil is changed. There are many types (or sizes) of oil filters for vehicle engines. Vendors of oil filters have information on which type of oil filter is compatible with a given vehicle.