I think the whole point of the original post was to point out the coking in the valves problem in the SS 2.0 turbo charged , direct injection engines.
So run what you brung.
I will ask why synthetic oil rises in price faster when the price of crude goes up on the stock market? Same with gasoline.
And don’t get me started on OPEC!

General Motors dexos Licensing Program
 

I found this information that I think will best serve to clear up the Dexos 1 Gen 2 question of which oil can you use in the 2.0 engine.

About dexos® | GM dexos® Licensing Program

Read the article and go to the bottom of the page and click on the Licensed dexos Brands. There are a lot of different synthetic oil's on the market that are suppose to be dexos 1 Gen 2 compliant. :twothumbs:

Coking on Turbo Bearings
 

This is an interesting article concerning coking in Turbo bearings. The article recommends letting your engine idle for 30 to 60 seconds before shutting the engine off. The article also discusses contamination which is why I think an occasional oil analysis is a good inexpensive preventative measure.

General Information

The coking problem with the 2.0 LNF is an intake valves coking issue. Really nothing to do with their turbo having any coking issues.

From their site:
"Welcome to Chicagoland Chapter GSCA our Chapter's website. Please take a few minutes to look around and see what we have to offer the performance Buick enthusiast. Our primary interests include 1965 to 1972 Gran Sports, 1984 to 1987 Turbo Regals, and Supercharged 3800 Buick powered cars while offering support for any performance Buick enthusiast."



Yeah, this concept has been discussed here before, consensus is that the Ecotec LNF is a different animal from the older turbo cars. The cool down is unnecessary. You can probably find those threads with the search function.