You probably wonder what the importance of viscosity in your engine is.
The viscosity will determine how easily the oil is pumped to the working components, how easily it passes through the filter, and how quickly it drains back to the engine. The lower the viscosity, the easier all this will happen. That is why cold starts are so critical to an engine because the oil is cold, and so relatively thick.
A fluid’s viscosity is important because it is directly related to its load-carrying capabilities. The greater a fluid’s viscosity, the greater the loads it can withstand. The viscosity of the liquid must be suitable for separating the moving parts under normal operating conditions (temperature and speed).
Knowing that a fluid’s viscosity is directly related to its ability to carry loads, one would think that the higher the viscosity of the fluid, the better it is. The fact is, the use of a high-viscosity fluid can be just as detrimental as using too light an oil.