No car requires premium gas anymore.
I included the cost of regular gas because even that showed the article was being disingenuous about cost even using those numbers.
Per a 2017 jalopnik article[1], any short term gains by using cheaper gas are likely to be lost because of decreased performance. While any short-term problems will likely be addressed by anti-knock sensors, long term problems aren't known. If you're that price-sensitive, buy a car designed for regular octane fuel.
[1] https://jalopnik.com/why-putting-regular-gas-into-a-car-that...
Our baseline fuel here is called "Premium Unleaded", despite it being the standard fuel and is 95 RON, which should equate to about 90-91 AKI meaning it lines up with your Premium gas.
We also have "Super Unleaded" at the pumps, which is 98 RON and should equate to 93 AKI in the US.
I guess that means we have no equivalent of your regular gas.
FWIW I've never managed to detect any benefit of using the 98 octane fuel, either in performance or fuel consumption. I've never owned a really high performance car, beyond a tweaked Saab 9000 Turbo running a higher boost, and that seemed to be happier on the Premium. I always assume that the 98 octane stuff is just a way of extracting extra money from gullible people, but I have no more proof of that than the anecdata from all the people who buy it and swear by it (probably because of https://en.wikipedia.org/wiki/Choice-supportive_bias )
You will just end up losing some fuel efficiency or power.
If you're paying for a higher-end car, it makes no sense to cheap out $.30/gal. Fuel costs, especially the difference from regular to premium octane, are so little in relation to everything else. While anti-knock sensors should avoid short-term damage, the long term effects aren't known [1].
[1] https://jalopnik.com/why-putting-regular-gas-into-a-car-that...
Look up engine knock.
The M3 has knock sensors, like everyone else.
https://www.google.com/search?q=bmw+m3+knock+sensor
If you look up engine knock on wikipedia, it will tell you the same
From: https://en.wikipedia.org/wiki/Engine_knocking#Knock_detectio...
"Due to the large variation in fuel quality, a large number of engines now contain mechanisms to detect knocking and adjust timing or boost pressure accordingly in order to offer improved performance on high octane fuels while reducing the risk of engine damage caused by knock while running on low octane fuels. "
That doesn't necessarily mean it reduces the risk of engine damage to zero. The engine still has to knock for the sensors to detect it and adjust unless it uses flex fuel sensors. Yes modern engines CAN cope with lower octane fuel than they were designed to use, but you would lose performance and run an increased risk of damage. If the manufacturer states a minimum octane rating you would likely be voiding some parts of your engine warranty by running the incorrect fuel.
Cars in the US are required to be able to run on 87.
Look up engine knock sensor.