Originally Posted by Gokhan
Originally Posted by Mad_Hatter
Originally Posted by Gokhan
"From a processing standpoint, modern Group III base oils are manufactured by essentially the same processing route as modern Group II base oils. Higher VI is achieved by increasing hydrocracker severity or by changing to a higher VI feed."
https://www.machinerylubrication.com/Read/493/base-oil-technology
Right, i get that the same equipment is used but the more severe processing a grp3 undergos produces a product with new molecular structures and PAO like properties. So from a performance perspective (lower pour points, higher VI and better resistance to oxidation and thermal breakdown), a grp3's more similar to a grp4 than it is to a grp2 - no? Doesn't this justify putting this unconventional base oil into a category all it's own and even going so far as to calling it a "synthetic", since it's more similar to a fully synthetic in almost every way than a grp2 mineral oil???
(I imagine this is what was debated, two sides of the fence, in the BBB ad case in re the definition of "synthetic")
That is correct.
However, there is no fundamental difference between Group II and Group III. Basically if you have a base oil and you measure VI = 119.49, it's called Group II, and if you measure VI = 119.50, it's called Group III, even though it's the same base oil with two different measurements giving slightly different results within random measurement error.
The critical quantity here is the VI. This is why base-oil manufacturers label their base oils as Group II, Group II+, Group III, Group III+, Group III++, etc. You can have a Group II and a Group III oil with VI = 118 and VI = 122, respectively, and you will see virtually identical performance. On the other hand, they make Group III oils with VI = 145 and higher, which is better than PAO VI. They will perform substantially better than cheap Group III. GTL has a very high VI as well, typically VI = 135 or higher.
This is why I don't fully agree with the National Advertising Division (NAD) of the Council of Better Business Bureaus siding with Castrol. The distinction (the VI = 120 limit) between Group II and Group III is fairly arbitrary, and these days most Group II base oils have VI close to 120; so, you're not getting a different oil when you buy a contemporary conventional oil with base-oil VI = 118 vs. a low-grade synthetic oil with base-oil VI = 122, such as the Castrol Edge products (excluding the Euro formulations), which use the lowest-quality (lowest-VI) Group III base oils they can find. They are at the lower edge of synthetic oils, right,
which puts you and your engine on the edge.
I see what you did there.....‚
I agree that the 119/120 is arbitrary and
kinda silly especially when you consider Chevron and others can mfg a grp2+ with a VI of 119 (or was it 115?)...but they have to cut it off somewhere, don't they? Maybe given the advancements in refining this calls for a revisit to the VI question, in re groups??
Fwiw I'm not suggesting grp2's are demonstrably inferior to grp3's or 4... I'm not making that case. It's been well proven that with the right additives a finished lube using grp2/2+ can rival grp3 finished lubes in many areas...so it's very capable and has some decided advantages over a grp3 or 4, like broader additive selection IIRC. Maybe that's why it's the go to base oil for what, 90% of the pcmo/hdeo industry??