What does 10w40 indicate about engine oil?
1 Answers
10W40 is the SAE standard viscosity rating for engine oil. This viscosity rating first indicates that the oil is a multi-grade oil. The 'W' stands for WINTER, and the number before the 'W' represents the oil's flow performance at low temperatures—the smaller the number, the better the starting performance in cold conditions. The number after the 'W' represents the oil's stability at high temperatures (i.e., its resistance to thinning)—the larger the number, the better the high-temperature stability. Below is relevant information about engine oil viscosity ratings: 1. Engine oils are specifically classified into 4 types for summer use, 6 types for winter use, and 16 types for all-season use. Summer oils are labeled as: 20, 30, 40, 50—the larger the number, the higher the viscosity and the higher the maximum applicable temperature. 2. Winter oils are labeled as: 0W, 5W, 10W, 15W, 20W, 25W. The 'W' symbol stands for Winter, and the smaller the number before the 'W', the lower the low-temperature viscosity, the better the low-temperature flow, and the lower the minimum applicable temperature. 3. All-season oils are labeled as: 5W-20, 5W-30, 5W-40, 5W-50, 10W-20, 10W-30, 10W-40, 10W-50, 15W-20, 15W-30, 15W-40, 15W-50, 20W-20, 20W-30, 20W-40, 20W-50. The smaller the number representing the winter part, and the larger the number representing the summer part, the higher the viscosity and the broader the applicable temperature range.
