Optimal Fuel Grades for TTV6 (Gen 3 Engines)

This used to be sort of true but a rarity today.
Low and High grade are stored at the gas station and for mid grade, the dispenser mixes fuel from the 2 tanks.

 

I was under the impression that mid-grade is a blend of premium and low. At least where I am. My grades are 85, 88, and 91 here in Utah so you could make 88 with a 50/50 blend of 85 and 91.

 

This^^^^^^^ and for what it's worth a lot of mid grade is being sold since so many newer vehicles are tuned to run on it.