Higher octane without an engine that can take advantage of it will just lead to poor mileage. In my case, I can increase the boost on the turbo and make considerably more power out of the same parts, but you’d be more limited when it comes to a naturally aspirated engine. There is more to worry about and it’s not that simple but E85 has a huge scene within the tuning community.

Premium isn’t better, just more resistant to pre-detonation, if your engine doesn’t make pre detonation more likely, you don’t need it.

My 08 turbo Subaru calls for it my 22 turbo Subaru doesn’t. if I put 87 in the 08, it won’t get very far, on the other hand, the 22 is just fine.