But the purpose of "octane rating" is resistance to detonation. "Octane rating" has no other purpose.Using an 85 in computer controlled engine, would conflict with operating parameters of powertrain. Regular octane fuel 87. Manifold pressure, temp, timing, all factors and conditions based on first element of equation 87 octane.
Given that cylinder pressure will be reduced at altitude, detonation is also less likely, and even if the knock sensor detects it, it'll pull timing.
I'd rather take a chance on "low" octane on an engine WITH a knock sensor, than one without.
It's not like gasoline has a set chemical formula. It's a mix of hydrocarbons that varies from one refinery to another, maybe from batch-to-batch depending on what happens to be in the crude oil at the time. And in North America, that rating system ("Pump Octane" or "Anti-Knock Index") is the average of two testing methods--Research and Motor. A fuel that scores well on one, but poorly on the other can have the same number posted on the pump as one that scores mediocre on both tests. One or the other may run better in a given engine, though.
The only thing we've got going for us is that they make a lot of it, and they wouldn't want to reinvent the recipe every time.
Last edited: