What type of octane I should use???

[SophieSleeps]

Originally Posted by bigsky2

So the burn rate, if you will, is the same across all octanes?

Then why... are there arguments that higher octane or lower octane provide better/worse mileage...

Because they are stupid.

Mileage is determined by how much fuel you use.
How much fuel you use is determined by your air/fuel ratio.
Air/fuel ratio is measured from your primary 02 sensors in your exhaust.
In closed loop operation, your car reads this Air/Fuel ratio and makes adjustments to injector duty cycle.
If your injector duty cycle is higher, you inject more fuel. If lower, less.

Running different octane has no effect on your air/fuel ratio.
Why? Because the ratio is AIR and FUEL.
So naturally it will have no effect on mileage.


If at all, I would think lower octane fuel would be better gas mileage because it is more likely to burn. Then you would have less unburnt fuel exiting via your exhaust. With higher octane fuel, it is less likely to pre-ignite or detonate so you have more a chance of getting unburnt/unused fuel (waste)