TIL my tires were 6 psi low and that was the whole reason my gas mileage dropped
I checked them at the air pump in Fresno on a hunch and it went from 24 to 27 mpg, so now I'm wondering how often everyone else actually checks theirs.
That "checked them on a hunch" part got me because I always figured tire pressure was one of those things that barely moves the needle. Then I actually tracked mine for a couple months and saw the same kind of jump you did, like 2 or 3 mpg just from air. Now I check them every time I get gas, which sounds annoying but takes two minutes at most.