High Altitude and octane rating

Okay, I have been through all the octane threads and believe the consenses is people like the higher octane rating better.

But how about for a Taco 4.0 running at 5000-8000 feet in the mountains? Does a higher octane really get you more?? Does the computer adjust for higher altitude (less oxygen)? Could I get away with 85 octane in the higher altitudes??

Anybody have a good scientific answer?? I sure do not!!

 

Thanks, I will use the mid-grade here too. I have used 85 and the engine runs fine. No pinging or missing driving at 6000'+. But a better fuel is always good, especially when mixing it with less oxygen.