Originally Posted by ammolab
If the engine is actively preventing knock/detonation on regular gas...IT IS designed to operate "that way"!
It just makes more HP on higher octane fuel. I would say that "Permium REQUIRED" engines are not designed to prevent
Knock on regular gas while "premium recommended" should be.
Depends. If the way they use to prevent knocking is open loop and massive retard / run super rich, it is going to use way more fuel, dilute your oil, and may shorten the cat / O2 sensor live. At least when they do that they are saying that "we are not confident with it, but if you insist we are protecting ourselves". Their engineers likely have done enough work to tell the marketing not to put that on the brochure.
It might make sense when gas was 99c for 91 and 79c for 87, but it does not make sense when it is 4.39 for 91 and 3.99 for 87 on a hot summer day at sea level, because running rich will likely use way more than that.