Oh, another lesson in tortured logic from BuickGN.
Japanese cars spec off-the shelf dino oil, not Redline.
European cars spec European oil, end of story.
Your description of the Astra as an "economy" car highlights your lack of comprehension of automobiles in general. It's in fact a sport compact, emphasis on "sport", since it comes with the European suspension package and oversize brakes from the factory, making it "sportier" than either of the wretches you drive. A Buick and a "modded" TL...not even a TL-S, but an old TL with botched bodywork.
I still can't get over the hilarious notion of a TL out lumbering around a track. People must just stare in amazement. I personally have never actually seen a TL on a track, seen TSX, seen Accord Coupe, but *not* a TL. I've seen Astra too, which in fact holds track a record at Nurburgring.
A tracked automatic TL with Redline, BBK and ~crazy~ suspension mods must hold *some* kind of record too, but I'm too polite to ponder that here.
I hope you are able to overtake all the Buick LeSabres on the track, in the luxury class your car fits into.