I have a few links on the topic of group IIIs that I have not posted on this forum.
My opinion is that group IIIs when used in engine oil blending are best left for 0W20, 5W20, and 0W30.
The 0W40s and 5W40s likely perform about the same whether group III or PAO.
The PAOs would be the best for 15W50s and higher, as group III base oils are very light.
I always thought that group IIIs spelt trouble for the specialized lubricant industry.
Interesting, 20,000 hours to 2.0 TAN for the turbine oils.
8,000 hours is one year of continous service.
The stability of those turbine oils make it ideal for motorcycle suspension fluids at $2.50 a litre for Shell and other brands of Turbine 32, or synthetic compressor fluids at twice that price.
(MX forks have to be cut down to ISO 15-27ish with an R+O 10)
I find this article very interesting ....
If you look at the Chevron/Phillips Chemical, print ads in "Lubes and Greases" magazine, they continually talk about the superiority of their PAO's in comparison to Group III basestocks. It sounds like they want to have it both ways.
I think the Group III stocks are best suited to formulating the 5w-20 through 10w-40 grades. The 0w-30/0w-40 grades generally require some PAO to acheive the low temp viscometrics, and the Group III stocks are too thin to make 15w-40 and 20w-50 grades without using some Group II stock.
I actually think a properly formulated Group III oil - with an optimized additive chemistry - can perform comparably to a PAO for perhaps 10,000 miles in a gas engine passenger car. Unlike the critics, I've actually tested Group III oils and done oil analysis testing on them. The Petro Canada and Amsoil XL-7500 Series products both performed very well in my tests. I have not tested the Shell Rotella T synthetic, but the oil analysis tests I've seen posted look fine.