What octane is everyone running on their cars? I know the minimum is 87 octane, with 91 recommended and 93 recommended for M cars.
I’ve ran 87, 89, and 93 octane and have felt no performance difference. Also, I don’t hear any knocking on any octane thanks to the knock sensors.
Car is a g20 m340i with a b58.
No one is telling you exactly why you should fill up with 91+ instead of 87. I’ll try.
Your engine runs a high compression ratio and a turbocharger, which requires fuel that doesn’t self ignite under high pressure. Higher the octane level, higher the pressure required for self ignition. So if your car states you need 91 and you use 87, your fuel is igniting before the spark plug even lights up (or midway during the compression stroke). This adds excess heat and stress on components in and around your cylinders.
“ECUs are smart enough. They adjust” - how does an ECU alter the compression ratio? Compression ratio is a function of bore and width of the cylinder and stroke length of piston. ECU alters other parameters trying to ‘minimize’ the risks. It’s supposed to be a failsafe and not for regular operation. In any case, your engine is running in less than ideal conditions when you fill up with 87.
Hope this helps.