Your owner's manual should recommend the right type of oil to use in your car. Five-w-thirty or ten-w-thirty s-j-c-f oil is used in most modern automobiles. The first set of numbers on a motor oil's label refers to how it should flow in different temperatures. Five –w-thirty should have the viscosity, or thickness, of a five-weight oil in winter and a thirty-weight oil in summer. Many people think the 'w' on the label stands for weight, but it actually stands for winter. If the oil is made for a gasoline engine, it'll have an 's' on the label. If it's for a diesel engine, it'll have a 'c'. The last letter represents a rating of the oil. A higher letter means a better grade. Consult a qualified mechanic in your area and your owner's manual to find out which type of oil is recommended for your car.