These tests make it easy for anyone to compare motor oils. Viscosity Tests Viscosity is the measurement of how thick an oil is at a given temperature. Volatility increases as temperature increases. Unfortunately, current passenger car motor oil test protocols do not include tests that measure high temperature deposit control, but since this is an important function for a motor oil it is worth mentioning. Significance Flash point is the lowest temperature at which a flame causes vapors to ignite.
Fire point is the lowest temperature at which burning is sustained for five seconds.
What It Means High flash and fire points are preferred. This is the most important characteristic of any lubricant. What It Means A high VI is desirable. Home Cold Crank Simulator Apparent Viscosity Significance Determines the apparent viscosity of motor oils between -40 F and 32 F and at high shear rates. What It Means Low values indicate improved cold temperature pumpability and flowability.