Got a confession to make...

I have been filling up with 87 octane fuel for a few years now. Totally due to the price of 87 octane as compared to 91 octane price. Well, the 91 octane price was a bit lower recently (at least a month ago, prior to the new 12 cent gas tax increase). So, I decided to see how much of a difference going back to 91 octane would make on the engine. Didn't realize how huge a difference in power and responsiveness it made! When I was using 87, the ECU would not allow me to accelerate real hard, without a retard of the timing. I thought it was a mechanical problem. The car is a lot more fun to drive now! I guess I have to suck it up and pay the premium price for more permagrin. I know, you can't go cheap on gas and tires.

Please see it in your heart to forgive me.

Hey Tony. Nothing to forgive. It was you who was missing out on the fun. It would have been interesting to compare gas mileage before and after the switch in fuel. My guess is that you'd see some improvement in mileage which would help to make up for some of the extra you're spending on fuel.

Glad you're getting the full enjoyment out of the car now.

I've read that using lower octane fuel results in lower MPG that typically offsets the price difference. Did you observe a difference there?

I havent checked recently (before going to 91). My mileage (mixed, but mostly stop lights in the city) is typically 16 to 17. I will check at next fill up and compare. Long trip freeway has been ~24 to 25.

i'm driving a 2016 ford edge with the 3.5 V6. i've filled the tank with all three grades of gasoline and definitely see a 10% improvement in mileage with the 89 over 87. not much difference when i go to 91.
the 10% improvement is empirical whereas the power is only judged by feel which could be my wishful thinking. 89 is a tiny bit less than 10% more expensive so it doesn't make much difference except that i can go a bit farther on a tank.

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MY 2000 S, Ocean Blue, Metropol Blue, Savanah Beige.
Bought June 2000 - Sold May 2010