I simply stated my experience. I've ran 91 (ethanol and non blends)92, and 93 octane in my car, switched back and forth to see if I was imagining things, and found that the car runs best on 93. Might just be the gas in my area I suppose, might be my car. Who knows?

 

So you're saying Ferraris are designed to run optimally on 91?

Being able to run on 91 doesn't mean 91 is the optimal fuel. That's my main point.

Ferrari wrote this because the fuel we use in the USA isn't the optimal fuel.

 

Are you saying our engine was designed as a high performance engine?

If you think you're car runs better with octane booster, by all means, go for it. I run nothing but 93 in my car.

But our engine isn't a Ferrari. It's part of a larger family of engines:

https://en.wikipedia.org/wiki/Nissan_VQ_engine

I think Nissan optimized our tunes for premium, but I don't think they "designed" it around 93, and then had to scale it back because our gas is crapp* and to make it safe for 91.

If you're looking for proof, I don't think there is any. You can go by what your tuner says, if that makes you happy, but the proof is somewhere in Engineering or R&D at Nissan.

 

^ Just using ferrari because it's easier to make the point with a more extreme example.

I think the best way to answer this question is to find out what the Japanese owner's manual says for G37 and 370Z. Having difficulty locating it online though.