To clarify, my conspiracy is that on 91 octane that the engine is designed for it is able to run leaner and hotter in the combustion chamber, which makes more NOx emissions than are allowed, so they just added a map to the ECU that limp modes the engine a bit on 87 so there's reliably no knocking and lower emissions, and they don't care that mileage takes a hit because nobody who buys a GTI will put 87 in it, because we are "enthusiasts". IE I'm saying I think the car can't pass emissions regulation on 91.
It's 110% a conspiracy theory. I could test it by going to a shop that does emissions testing once on 87, and once on 91, or by carefully logging certain parameters through ODB2 on both types of gas. I just.... haven't
Something to think about, now that so many decades have passed since the octane test methods were fully standardized in the USA;
Auto and oil companies have had the same number of decades to come up with more "interesting" ways to game any numbers involved.
The EPA didn't even get concerned with gasoline until relatively few decades ago, and their input has been more from the standpoint of a "pure" bureaucracy.
It's 110% a conspiracy theory. I could test it by going to a shop that does emissions testing once on 87, and once on 91, or by carefully logging certain parameters through ODB2 on both types of gas. I just.... haven't