Why did all the local Shell stations suddenly get into lockstep yesterday?

Factual Questions
1

[Gasbuddy map-type in “32250” for the zip]

I frequent the one at the south beach, which almost always has premium on sale for +/-10 cents less than the other Shells (prob. because of all the luxury/high performance vehicles there-I drive a Civic SI). Drive in there to fill up, and am flabbergasted that that was no longer the case, and to boot of all the Shell stations I visited yesterday ALL of them had the exact same prices (well, one had regular at -2 cents-big whoop).

Asked two clerks at two different locations, and they both said that the stations were owned by a local gas conglomerate which sets the prices (I had assumed that the Beaches one at least was a franchise). Usually the prices for plus and premium are all over the map; my hypothesis then would be that the holiday brought in a bunch of out-of-state drivers who would be ignorant of the best local deals. They will probably all diverge this weekend, just though it worthy of curiousity…

2

I don’t know how this factors in but I have heard that Ethanol, which is cheaper the gasoline, can and is used to raise octane rating, so it is actually a cheaper product that sells for more.

3

I have a family member in the industry and they say their prices at all their stations are almost always set according to the competitors across the street. Even if they take a loss, they have to stay close to the competition. My guess is that your local shell conglomerate was closed for Thanksgiving and the person in charge was working from home and just set all the prices the same instead of looking at each station individually.