The best synthetic motor oil for a car should have the appropriate viscosity, or thickness, and meet the standards of the automaker, according to Cars.com. Reference the owner's manual to determine the correct viscosity. Motor oils that include the American Petroleum Institution certification typically meet the standards of many automakers.
Motor oils that meet the most current performance standards are certified by the American Petroleum Institution and include the organization's logo on the container, states Cars.com The appropriate viscosity required by a vehicle is determined by the Society of Automotive Engineers. The use of the wrong type of motor oil can lead to damages that may void the warranty of the car.