Let's talk about the "viscosity" which is the most important indicator of motor oil. One of the most common indicators of motor oil viscosity is the SAE value of motor oil. What do you usually hear about OW-20 and 5W-30, right? There are five common numbers in front of W, which are 0, 5, 10, 20, and 25. The smaller the number, the lower the applicable ambient temperature. There are also 5 common numbers behind W, which represent the highest temperature applicable to the motor oil, which are 20, 30, 40, 50, and 60, which represent the viscosity of the motor oil. This is also the case in motorcycle oil. Most of the motor oil used by European and American motorcycles such as BMW is 5W-40, 15W-50, Harley 20W-50, KTM 10W-50, and Ducati 15W-50. The motor oils used by Honda and Kawasaki are 0W-30 or 10W-40. Therefore, it can be seen that European and American car manufacturers pay more attention to vehicle performance, so the viscosity of the design oil is slightly higher.