What petrol are you running?

Before this thread goes off the rails... In Europe, the octane rating on the pump is simply the RON figure. America, by contrast, uses the average of the RON and the MON figures, called the AKI (anti-knock index) or PON (Pump Octane). Thus, 97 octane “super unleaded” in Britain is roughly equivalent to 91 octane premium in the United States.

Ethanol percentage in the US is both seasonal and regional.

 

Correct. There are gas stations that carry ethanol-free gasoline, but they are few and far between here in the US. At least in Texas.
https://www.pure-gas.org

In my Cali, I run exclusively 93 octane (using the (RON+MON)/2 system we have here) Shell V Power. I am pretty sure it comes with 10% ethanol.
No issues. To be honest, I once goofed and put half a tank of 88 octane in the Cali, before realizing I f***d up. Add half a tank of 93 as a chaser, and
then drove it around to burn the tankful of gas (any excuse to drive the F-car! ) . Nothing blew up, no CELs, no cease & desist letters from Ferrari SpA!

T

 

Here in California, we've been using up to E10 fuel for decades in all cars on the road. My 2016 California T has about 20k miles on it with 91 octane. Ethanol is not required in California but it is the most popular oxygenate for fuel for smog reduction purposes and California does require an oxygenate.

 

Any modern car will adjust the ignition and timing based on the fuel sensor. Regular grade fuel won't damage the car, but the performance might deteriorate. If the car is stored for longer periods of time, premium grade fuel has proven to maintain its condition quite a lot better, so that's a no brainer.

As a rule of thumb I always fill the best grade available. I try to fill at branded stations such as Shell, Esso, BP etc. and not unknown names.

If only cruising around lesser quality fuel does the job for me. If the car is worked hard on a track day or similar situation, premium is a must for my personal peace of mind. Even though I have witnessed a Ferrari dealer running a 488 Challenge on regular pump fuel...