And that's exactly where i was wrong :-)
On many modern cars, high octane gas gives you more boom. They are designed for high octane gas, but the engine management computer is able to detect low octane gas and prevent damage from predetonation-- giving up some power.
>They are designed for high octane gas The vast majority of modern engines are designed for 87 octane, and not downrated to 87 octane, because that would give you poorer performance than a clean sheet 87 octane design, and single digit percentages matter here.
There's a whole lot of cars that say "Use premium fuel only" with compression ratios of >10.5:1, but rely upon anti-knock sensors to retard timing (and adjust mixture) to avoid detonation with 87 octane fuel.
I was a professional mechanic around that time, and I had coworkers that thought that not only would high-octane gas give more power, would also swear it increased fuel mileage. Neither is true. High-octane fuel has less energy per gallon than lower octane fuel, it can’t give better mileage. (Now, “mechanic” != “engineer”, but c’mon, guys.)
[0] Yes, Captain Pedantic, I’m aware of knock sensors and computerized ignition timing. It was a quarter century ago.
This stuff started to show up in the 1970's-- the 1981 280ZX Turbo my dad had was equipped with a knock sensor and would retard timing and add fuel.
By the mid-90's this was relatively common.
But adding high-octane gas to a normal engine doesn't make it go any more boom, in fact, it goes less boom because it doesn't burn as much when it booms.
Modern engines can be designed to advance or retard timing based on knock, so they can run on different octanes and provide different power curves.