I have a 2004 Ford Crown Victoria that was a police car, 266K miles on it, it’s on it’s 3rd transmission (replaced twice before I got it—I just got $150 junkyard transmission for it, it lost 4th gear and I suspect that it just a valve body problem), but the original engine.
I use E10 or E15 gas in it. I’ve tried a 50/50 blend of E85 and E10 in it, too. It ran fine off that, but anymore than a 50/50 mix and it’ll set a lean code because the fuel trim exceeded 25%.
Don’t usually bother with E85 because it’s usually not enough cheaper than E15 to be worth the fuel economy penalty...but E15 is often cheaper enough than E10 that it is (the fuel economy penalty for E15 is, in my experience, insignificant, you won’t notice it).
Those Crown Vics are impressive.
I’ve ridden in a few that were taxicabs down in Florida with over 400,000 miles.