I found the octane matters little for mpg. The 2.0T does have more pep with higher octane.
I've been mixing E85 and 87 octane. I mix 30% E85 and 70% 87 octane for about 93-94 octane. Cold start is good so far at 25°F degrees but mileage does suffer with E85.
2016 Envision Prem ll