Just drove from Nebraska to Chicago.
On the way out I filled up with 87 octane, no ethanol. Drove 60-65mph. A/C on. Family of 4 and a weeks worth of crap in the trunk. Result, 23.5mpg.
On the way home I said screw it. Filled up with E10 89 octane 'cause it's cheaper. Drove 70mph 'cause I was ready to be home. A/C on, etc etc... Result, 25.8mpg.
Uhhhhhhh... ???
89 octane will burn a bit cleaner.
my aurora will get 17 on 87 octane and 20 on 93 octane
My brother noticed in his non-p71 crown vic that he got better gas mileage with higher octane (the station was out of regular, he needed gas).
Otherwise, is there a possibility that the way home was more downhill? or that you had a tailwind?
what year was it? I was under the impression mine didn't even have a knock sensor, therefore low compression and retarded(relatively speaking) timing, all of which would add up to better results on low octane gas. At least that's how I understand it.
They do better with the ethanol because of high fuel temps. I see the same mileage gain as you did going from 87 to E10 87. I run E10 exclusive now.
1999, And it was just sold today.
"retarded" is such a mean word. 
I either run advanced or "Special" timing in my Miata.
lol.
that's counterintuitive to me about the e10 thing though. ahh well. not gonna argue with results. I'll see what it does in town. been getting 18-20 on the plain 87 octane up to now.
I once got 27 in my non-P71 "aero"-vic (1992). From Elkhart Lake Wisconsin to Kalamazoo MI... I was pretty happy!
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