Within each viscosity grade, quality scores are ordered from highest to lowest. The oil with the highest quality score is given a rank of ONE. The second highest quality score gets a TWO, and so on till the last oil within a viscosity grade category is ranked. Thus, the the lowest motor oil rankings are the highest quality oils within that viscosity and the highest ranking numbers are the lowest quality oils within that viscosity.
Since this ranking is done WITHIN viscosity grades, if you are viewing multiple viscosities at once within the grid, you will often see two or more oils (each of a different viscosity) which will have the same rank. Now that you know those motor oil rankings are specific to each viscosity, this shouldn't be at all confusing if you're viewing a list of oils that contains multiple viscosities.
The motor oil rankings are just an additional piece of information that can be used to most accurately compare the quality of oils. In some cases it may not be all that useful. In others, it may be the one piece of information that allows you to finalize your decision. Use it as you see fit, or hide it from view, using the hide columns feature (explained in the Video Tutorial).
And as you can see with these Diesel oils above, zinc levels alone do NOT establish their wear prevention ranking. The zinc levels are randomly up and down, relative to the ranking order. And as you will see in the link to my motor oil ranking list below, zinc levels clearly have NOTHING to do with an oil’s protection capability or ranking order. Also, anyone who has followed my motor oil testing this year, probably noticed that these Diesel oil “Load Carrying Capacity/Film Strength” psi values are rather low, with an average value for the whole group of only 72,408 psi. This number would put an oil for gasoline engines, only in the MODEST PROTECTION category (60,000 to 75,000 psi).