Most gas stations here are discount retailers. The Shells and Exxons are a minority and are considered a premium. Their prices rarely have huge swings, but also tend to be the highest consistently. QT, Racetrack, Costco, Walmart, Tom Thumb and Valero are the main retailers in the DFW area. They keep maybe a 2 day supply that has to be constantly replenished, thus the price changes every day if not twice a day. This is also due to the fact they pay upfront which is why they raise(or lower) the price prior to the gas being shipped. With the exception of Valero, QT, Racetrack and others are purely retailers. Valero is the largest refinery operator in Texas as well as the largest owner of oil pipe infrastructure in Texas. So as far as their gas goes they control it from the refinery to the pump. They also sell it to other retailers like QT and Racetrack.
So what happens if the price is cheaper one day and many more people buy gas that day to take advantage? It shortens the supply availability and causing either a shortage or a need for an “hot shot” delivery. That causes prices to go up.
Also this is fact. QT sets their morning price at a certain time and then updates it at a certain time in the afternoon. The Costco on Matlock in South Arlington, sends an employee up a few blocks to the QT to check the price in the morning then comes back to put theirs at a penny less. Then they check it again in the afternoon to make sure they are still a penny less.
Yes the Texaco/Chevron, Shell and Exxon/Mobil stations have to set the price from their regional headquarters even if they are a franchise. That is due to the company controlling the purchasing and deliver of the gas not the station. They could run out of gas and wait for days because they are not going to get anymore gas until the scheduled delivery comes in. A QT general manager has to constantly watch his inventory to make sure his Just In Time inventory method is in smooth operation. Otherwise they could be out of gas and have to pay a higher price from the distributer/refinery to get a delivery sooner than scheduled.
My apologies for thinking you were naive. The station I was referring to is a Shell convenience station, and I believe their price is set “from above”. It’s pretty busy and they pump a lot of gas. I really doubt the 394_9 price caused a run. As I say, since it had been rising steadily, the drop from 399_9 was as likely to inspire hopes for a further drop as anything else. At any rate, why would it go down $0.05 and then up $0.21 ? I regard it all as happenstance - like gusts of wind in a storm.