It looks like the upswing is on Mon/Tues, then with a slower downward trend for the rest of the week. And the weekly fluctuation is absent during price declines, you just see the “rest of the week” trend continue, without the uptick.

My first thought was “people buy gas when they get their paycheck”, but that doesn’t work.

Now, I’m thinking “when the station tanks are refilled”, or something like that. (distributers setting a price weekly?)

The maps, charts and graphs are very educational. And studying the charts really makes me wonder why Indiana and Ohio gas prices have a weekly cycle that doesn’t show up in any other states - as far as I can see.

But am I the only one that thinks about these price differences in percentage terms? John’s example above ($0.15 savings by going to NJ), when the “base” price is around $3.80 amounts to a 4% difference. The map shows a 15 cent difference between “lowest” and average just in my PA zipcode. Still, at the level of a penny or two /gal, it’s hard to get worked up over the “savings”.

Just a rough calculation: if you use less than 4% of a tank to fill up at a station that’s 4% cheaper, it’s a net win, otherwise not.

Try an example:
Smallish sedan, 14 gal tank, 25mpg, so a 4% difference in price breaks even with a 14mile total detour. I think the cheap station is just barely in that range for me. Most of the others are within 5-cents in price, so only 1.3% difference and worth a 4.6mile (roundtrip) detour.

As the saying goes, YMMV.