Obviously, the ability to flow readily is critical to start your vehicle's engine in brutal cold, and calls for a lower viscosity, such as 0W or 5W viscosity grade. For protection against high engine operating temperatures, oil must be able to function and provide the needed lubrication. When the vehicle is operating in summer heat, with temperatures above 80 to 90 degrees day after day, the need is for a high viscosity oil. These oils carry the low temperature flow, and high temperature lubrication properties of the two oils, such as a 0W-30. The issue of engine oil volatility is an important one to every car or truck owner, yet few know about it.
Volatility is related to viscosity.
Volatility is defined as the characteristic of liquids to become a vapor when heat is applied. To meet the federal government's fuel mileage standards, auto makers tell owners to use lower viscosity oils. Unfortunately, low viscosity oils tend to evaporate more easily than high viscosity oils. Less oil in the pan results in higher engine temperatures. Higher oil temperatures lead to greater evaporation, more oxidation, more deposits and shorter engine life.