The following article is intended to help you make a choice based on more than the advertizing 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. These measurements are taken at specific temperatures. The W means the oil meets specifications for viscosity at 0 F and is therefore suitable for Winter use.