I’ve actually never experienced the, “California gas sucks” issue that car people from the mid-west talk about, have never had an issue with it. ¯\_(ツ)_/¯
Not that it matters when everything made for "premium" is tuned for 91 from the factory anyway, not 93
1) Few refineries make it, so it's MUCH more expensive. But if you're living in California, it is easy to miss because EVERYTHING is much more expensive.
2) Mileage is generally poorer, due to the mandatory ethanol mixes. But some places also usually mix in ethanol, and the difference is usually in the 10-15% range. So unless you have a good A/B comparison going, it's also easy for it to blend in with all the stop and go driving, and terrible road conditions.
3) Mandatory Ethanol means generally very poor storage characteristics. Which considering how much driving happens in California (and how dry the climate is in the populated areas), most people won't notice.
So does it suck? Comparatively, definitely! Is it likely to be noticed unless you're very aware and have experience with other options? Nope.
In the case of my vehicle it results in low/rough idle and positive fuel tank pressure which otherwise do not occur either at lower elevation or with ethanol-free fuel at elevation.
No idea about 240z specifically, but at least things designed for sustained high performance (like aero engines) tend to use valve seats made from some wear and temperature resistant alloy like stellite or brightray.