10w30 is thicker than 0w40 in low temperature. 0w40 is thicker than 10w30 in high temperature. Am I right? Then... what temperature is the turning point ?? 0w30, 5w30, and 10w30 have same viscosity at high temperature. Am I right? Then... what is the minimum temperature that they have same viscosity ? I know they are different at winter start. Are they also different at summer start?