http://gasprocessingnews.com/feature...tural-gas.aspx
This article was written by Shell people so a bit of an advert, but, still an interesting read. I've seen elsewhere that GTL base oils are better than other group III oils and can be as good performing as group IV.
Interesting point of the terminology is that PAO's (Group IV) are made from ethylene gas which is a hydrocarbon but still called man made.
Bunch of useless information but fun none the less.