Originally Posted By: Johnny2Bad
With conventional base stocks the multigrade oil that needs the fewest and least robust Viscosity Improver (VI) additives is 10W-30 so on a budget that should provide the most stable oil at the least cost.
5W-30 (or 5W-xx) is really a premium additive package in a conventional oil. I can see how a hydrocracked (base III) 0W-30 "synthetic" could compare in price since synthetics need fewer VI's to meet a given viscosity.
Winter viscosity is so regional that what people are used to using is what they will buy; I can see 5W-30 being a popular choice in some areas and not so popular in others (without regard to what actual winter viscosity is ideal).
For example someone posted about 0W-xx being ideal for "Alaska" while elsewhere someone mentions how diverse Texas is when it comes to cold overnight lows.
Well, Alaska is twice the size of Texas and has a much wider temperature variation. The majority of Alaskans live in the Panhandle which experiences mild winters, much warmer than, say, North Dakota.
On the other hand, inland and to the north, Alaska really does experience the temperatures everyone in the lower 48 thinks it does (although very few Alaskans actually live there).
5W-xx is totally appropriate for Juneau in winter, 0W-xx is totally appropriate for Northeast Montana.
Your wrong about 10w-30 having the least amount of VII. Each grade will be formulated with a different grade base stock depending on the characteristics desired.
So it's entirely possible that a 0w20 could have less VII than a 5w-20. It all depends on the specific base stocks being used.
So it's entirely possible that a 0w-30 may have less VII than the same brands 10w-30,it depends on the combination of basestocks used by the formulator.
If all base stocks were the same viscosity to start then yes it makes sense that more VII would be required as the winter rating decreased however since basestocks can be made in a wide range of specific gravities and those gravities blended to the point where it's possible to minimize VII use to near zero it's inaccurate to assume the higher the winter rating of a grade naturally means more or less VII are required to achieve that winter rating.
Just sayin
