Yeah I guess you didn't read the follow-up to this situation.
I guess you did't read this part:
“Manufacturers say that drivers have to comply with the terms of the warranty, and the warranties say that you need to use 87-octane, period,” said Dan Gage, spokesman for the Alliance of Automobile Manufacturers, a trade group that represents 12 large automakers. “Eighty-five (octane) should not be used under any conditions.”
What part of "Eighty-five (octane) should not be used under any conditions” do you not understand?
Also this:
Volkswagen engines aren’t tested on anything lower than 87-octane, Schmidt said. To meet federal emissions and fuel economy standards, the industry is moving toward smaller, more efficient engines with turbocharged, direct-injection systems, said Stuart Johnson, a manager at Volkswagen who focuses on regulatory issues.
“From an industry perspective, (South Dakota’s proposal) is a step in the wrong direction,” he said. “If anything, in the future, we’re asking for more octane.”
Enforcing warranty terms in cases of engine damage that was caused by low-quality fuel would be difficult but not impossible, experts say.
This damage could emerge only after years of use, and a typical factory warranty might have expired by that time, Gage said. He declined to comment more specifically on how warranty voidings could be determined based on fuel use, saying it would depend on the manufacturer.
“How would they later prove that? I suspect they would have to build a case,” he said.
Calls to several local dealerships to discuss the warranty implications of using low-octane fuel were not returned.
Using low octane at high altitudes made more sense before cars had barometric sensors. The problem is, the car knows that the barometric pressure is lower so it advances the timing. But it has no way of knowing that you filled the tank with fuel below the minimum expected octane until it senses detonation and, as the article pointed out, the detonation sensor is an emergency measure only and shouldn't be relied upon for normal running. After detonation happens the engine management must dial back the timing and performance suffers compared to fuel that meets minimum standards.
Modern cars are very different from gramps '56 Chevy.