>   So. Is it ok to run out the full tank with the higher octane?

Without getting into too much detail, octane rating is basically how
evenly the fuel ignites. Most engines are fine with 87. Some high
compression engines need higher octane to prevent pre-ignition. The
2.1 wasserboxer could probably run on 40 octane. Higher octane gas
than you need shouldn't make any difference. That said, I had a '67
Dodge Dart that ALWAYS ran better (and got better mileage) on the
lowest quality gasoline I could find. Perhaps the cheap stuff was
adulterated with kerosene, or the expensive stuff had whatever fancy
additives, and that old 273cid, 2bbl carb, mechanical point ignition
detroit water pumper was partial to kerosene over fuel injector
cleaner.  Mysteries of the universe...

--
John Bange
'90 Vanagon - "Geldsauger"