A week ago when I went to fill up my car, as I took the nozzle out of the pump the hose smacked the 89 button which turned it on and I couldn't get the pump to switch to 87. I had enough fuel points that I was getting a free tank anyway so I went ahead and just got the 89. My fuel mileage for the following week was awful. My average was 11, and the highest MPG I got was 15 on a highway trip.
Now 2 days ago I filled up again, this time with 87, and almost immediately my city average went to ~16 and it got 24 on a highway trip. I'm not running a custom tune or anything crazy, so why did running 89 octane bring my MPG down so much?
Now 2 days ago I filled up again, this time with 87, and almost immediately my city average went to ~16 and it got 24 on a highway trip. I'm not running a custom tune or anything crazy, so why did running 89 octane bring my MPG down so much?
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