My gas engine cars warranty was ALSO extended to 150,000 miles. There was a law suit filed. It originated because an engine had sludged up by running the distance indicated by the FSS with dino oil.
I don't think that there's a mandate to run syn in these cars, it's just that the FSS is "calibrated" for them. I run syn and change it in between dealer visits anyway.
Have a great day,
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