Found this little tidbit in the manual.

2.3 gallons E85, rest pump gas. For people (like me) who only have access to 91 octane, this mix gets us to 92.8 octane, which is close to what the fuel cap calls for (93 octane).

I just did this mix and definitely felt a performance boost compared to pump California 91.





https://www.miniusa.com/content/dam/mini/PDF/archiveownermanuals/MY21/2021_HARDTOP_2_DOOR.pdf

 

Nice! Here in Maryland, we have 93 at the pump. However, I will give this mixture a shot next time I am at my local Sunoco which has both E85 and 93. If I do 2.5 gallons of E85, I will be at 94-95 octane.