In the recent thread on NOACK...Gokhan posted an informative graph which showed that 'New Yubase' base oil approaches the performance of PAO and GTL base oils (despite being Gr.III...I believe). Yubase is made by SK lubricants of South Korea who is one of the world's largest producers of Gr.III base oils. I know that Motorcraft 'full synthetic' SM rated that was on 'CLEARANCE' a few years ago at AA said "Product of Korea....Blended and packaged in the USA" on the label so I'm sure it used Yubase.. (although that was probably not 'new' Yubase being that it was from the SM era). Does anybody know which companies (products) are using 'New Yubase' base oils today? Also, I didn't realize that there were 'subclasses' of Gr.III oils....Gr.IIId...Gr.IIIcâ€¦.Gr.IIIb etc...Does anybody know the significance of these letters after the Gr.III?