Needed to fillup the Mustang the other day. Saw a Sunoco and a Marathon next to each other showing the same price on the board for regular. Pulled into the Sunoco and noticed this trickery....
Notice how 93 is 30 cents more expensive than 87 because there are 2 levels between them. The neighboring Marathon doesn't offer 91 so their 93 was 3.859. This is the first time I've seen a gas station charge 10 cents more for 93 than 91. I know of a Sunoco back in MA that only charges an extra 2 cents more for 93 (which seems more reasonable).
But yeah, I didn't fill up here. I went over to the Marathon next door.