The following article is intended to help you make a choice based on more than the advertising hype. This is an average of the actual physical and a few common chemical properties of their oils. This information is available to the public through their distributors or by writing or calling the company directly. I have compiled a list of the most popular, premium oils so that a ready comparison can be made. If your favorite oil is not on the list get the data from the distributor and use what I have as a data base.
Viscosity is the measure of how thick an oil is.
This is the most important property for an engine. An oil with too low a viscosity can shear and loose film strength at high temperatures. An oil with too high a viscosity may not pump to the proper parts at low temperatures and the film may tear at high rpm. The higher the VI, the less change that occurs and the better the protection. Flash point is the temperature at which an oil gives off vapors that can be ignited with a flame held over the oil.