Turbo, Fuel Octane and Altitude

HardRightEdg

US 2020 CX-5 Touring AWD Soul Red
Where are you getting E10 97 and 99 octane fuel?

As for ping, I've had opportunity to test this, but I suppose there is lower limit to ignition retardation--your 2004 would have had knock sensors-- that would make pinging pronounced; e.g the PCM detects the knock from the knock sensor, but can't make further timing retard, and thus only highly octane fuel would solve.
My bad. That was supposed to be E10 87 and 89. That post has been corrected.
 

HardRightEdg

US 2020 CX-5 Touring AWD Soul Red
Think I should just fill up with Costco Premium along the way and not give it a second thought.
That might require some planning. Costco has only about 600 stores in the US, fewer than the number of Tesla charging stations. See the the following map and store database:


Even if you go by a city that has one you might still have to go quite a ways off your desired route.