To help oil do its job, refiners add dispersants, which keep contaminants suspended in the oil, plus rust inhibitors, detergents, and antiwear agents . We've also found no advantage in using oil additives such as STP or Slick 50 .
Viscosity is the oil's ability to flow at a given temperature.
Use the grade your car's owner's manual suggests for your climate. The service grade, on the label, is based on an American Petroleum Institute certification program to ensure that an oil protects against deposits, wear, oxidation, and corrosion. What you'll pay Some people save money by changing the oil themselves. Moreover, disposing of used oil, which poses an environmental hazard, means taking it to a garage or other safe site. Dealers tend to be the costliest venue for oil changes, but lately we've seen that some are offering discounted oil changes as a way to build business for their service department.