what is group III+ ?

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asiancivicmaniac

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I don't know much about base stocks, only enough to know group III is kind of a synthetic and IV and V are synthetic. But what is a group III+ base stock? I ask because I have several gallons of Shell Rotella T 5w-40 that I plan to use after my Auto-rx rinse so I'm curious. How does group III+ compare to PAO and esters?

Now a question more specific to the oil. I've read that Rotella syn has influences of Shell Helix. What is it?

Thanks
 
Does the Rotella T 5W40 mention that it is Group III+ ? Although I may be wrong, I have only heard of Group II+.
Should there be a Group III+, maybe it's Group III with some PAO mixed in.
 
stolen from MGregoir:

Technically, the difference in definition between group II and group III is that group III has a higher viscosity index than group II, group III being greater than 120, II being between 80 and 120.

Group II+ is defined as being on the higher end of the group II spectrum, viscosity indices just barely below that of group III, and group III+ is where the XHVI type oils come into play with VI numbers over 140.

Group III+ oils are so heavily processed that I would not feel guilty calling them synthetics in the same catergory as PAO and esters. It just so happens that it was synthesized from crude.
 
Group III+ is not an official designation but is generally used to describe base oils made from slack wax through a wax isomerization process to a VI of 140+. Shell and ExxonMobil make these base oils. For more information, see:

http://www.exxonmobil.com/apps/refiningtechnologies/lubes/mn_mwi.html

The NAD conclusion in 1999 that "Group III" can be called "synthetic" was actually specific only to the Group III+ being used by Castrol at the time. Marketers of standard Group III, however, decided the ruling applied to their products as well. As a result, the definition of "synthetic" has been diluted to a meaningless marketing term that turns on a single VI point, i.e. 120 versus 119.

I would consider Group III+ to be equivalent to PAO from a high temperature stability view point.

Tom NJ
 
Originally Posted By: chevrofreak
Group III+ oils seem to shear quite badly, though.


data/basis??? Havent been keeping track and would like to know more.
 
Originally Posted By: chevrofreak
Group III+ oils seem to shear quite badly, though.
Does base oil shear, or do the viscosity index improver polymers get sheared? I think the latter, and very little when high quality/high cost VIIs are used.

This chart from Chevron compares the properties of three Group III base oils. As can be seen, there are performance differences. Because the "+" on a group number isn't official, unless it is unofficially adopted by several oil companies like II+ has been, it can be used any way the oil company chooses. Chevron calls their's Unconventional Base Oil (UCBO) and the others are called Very High Viscosity Index (VHVI). By the way, ConocoPhillips is a major importer and distributor of Korean Group III which might be the Asian VHVI listed.
http://www.chevron.com/products/sitelets/baseoils/comp_med.aspx
 
Originally Posted By: Ken2
Originally Posted By: chevrofreak
Group III+ oils seem to shear quite badly, though.
Does base oil shear, or do the viscosity index improver polymers get sheared? I think the latter, and very little when high quality/high cost VIIs are used.

This chart from Chevron compares the properties of three Group III base oils. As can be seen, there are performance differences. Because the "+" on a group number isn't official, unless it is unofficially adopted by several oil companies like II+ has been, it can be used any way the oil company chooses. Chevron calls their's Unconventional Base Oil (UCBO) and the others are called Very High Viscosity Index (VHVI). By the way, ConocoPhillips is a major importer and distributor of Korean Group III which might be the Asian VHVI listed.
http://www.chevron.com/products/sitelets/baseoils/comp_med.aspx


How much VII do RTS and M1 0W-40 have?
 
Originally Posted By: wannafbody
Mobil 1 0w40 doesn't shear too much because it starts out as a thin 40W oil.


It's actually a 0 weight oil functioning as a 40 weight...
 
Originally Posted By: BoiseRob
Originally Posted By: wannafbody
Mobil 1 0w40 doesn't shear too much because it starts out as a thin 40W oil.


It's actually a 0 weight oil functioning as a 40 weight...

You might want to look up pour point depressants.

And I think 0W40 shearing is mostly from VII.
 
Originally Posted By: BoiseRob
Originally Posted By: wannafbody
Mobil 1 0w40 doesn't shear too much because it starts out as a thin 40W oil.


It's actually a 0 weight oil functioning as a 40 weight...


That's not how it works.
 
Originally Posted By: chevrofreak
Group III+ oils seem to shear quite badly, though.


Not according to my recent ~5000 mile UOA on RTS 5w40 in a Jeep 4.0. Still within spec.

There's still a lot of talk about shearing, but with the quality of today's base oils combined with better VIIs than ever, I think its mostly relic of the past. Or at least of poor oils.
 
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