CX-9 2.5T drives better with 91 Octane

Mine also hangs around 18-20 MPG (18 in the dead of winter, 20 in summer temps). 90% "city" driving, with a very short 80km/h stretch on my commutes to and from work. I would expect better numbers if you're on the highway more often, but that can easily be negated if you're a little heavy in the foot. Admittedly, its really easy to push the car without noticing it

I called Mazda. They stated 0 testing has ever been done on 91, but that the relationship is linear and based offnof 02 readings....which Infind odd..but ok

Unobtanium said:

I called Mazda. They stated 0 testing has ever been done on 91, but that the relationship is linear and based offnof 02 readings....which Infind odd..but ok

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Interesting thanks. I'm not sure what percentage of the country carries 93 octane but I never see it anywhere in the intermountain west. Mostly 91 and occasionally 92 in Montana. So I'm going to go with 240 HP on 91 octane. I wonder why Mazda chose 93 octane as the measuring stick? Bigger power number I guess.

Montanaman said:

Interesting thanks. I'm not sure what percentage of the country carries 93 octane but I never see it anywhere in the intermountain west. Mostly 91 and occasionally 92 in Montana. So I'm going to go with 240 HP on 91 octane. I wonder why Mazda chose 93 octane as the measuring stick? Bigger power number I guess.

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I only use non-ethanol fuel. For a while, no 93 octane non-ethanol was available where I live. It's back now and the Mazda rides silky smooth getting 22mpg in 90% city driving.

It makes sense on a smart ecm vehicle that it would get very slightly better mpg on fuel that gives more power. At any given power requirement on the road you are a few percent smaller throttle opening..

But yeah I'll stick with my 87. I don't think you can beat it dollar wise despite that. I think lately ours has been at twenty and a half.

The 22 on ethanol free don't surprise me either, that ethanol stuff has good octane boosting effect, but its not got much energy in it. My gallon probably has 5% less calories versus yours.