Over time I've noticed there's major changes in gas prices in groups and I surmise this to be a regular price change in a regular cycle of changes. But I've never really tracked it to pin down the actual day of the week (or the time of day) that this behavior can be counted on to occur. Of course not everyone is going make changes every time and it won't be the only time changes occur, but it is the time most frequently one can count on changes to occur. I feel it's about twice a week, on Thursday afternoons and again on Monday. Early in the day. I may be way off base, but that's my perception.
So, if there is regular time frames that could help plan when to cruise my routes I appreciate hearing from the lurkers out there that know.
Gas price changes on Friday
I agree with your general observation that prices tend to be more stable Weds through Fri. I've studied retail prices and tracked wholesale prices for more than 12 years now, and the only pattern I've noticed is that when Arco moves, eventually EVERY station has to move. There is no "usual day" when we see maximum price movements across all brands, although in my experience, Wednesdays through Fridays seem to be the most stable days of the week when we see the fewest changes.
However, there is one very good reason why prices do change over the weekend ...
The probable reason for any "sudden" changes on Fridays is that the spot market closes on the NYMEX and in LA early Friday afternoon and remains closed until Monday morning.
(spot gas is "pure" unblended California Air Resources Board Oxygenate Blend gas without the ethanol or detergent).
If there is a lot of surplus CArBob being dumped on the market, then the price of fuel will go down on the street. If the price of CArBob jumps suddenly on Friday it suggests a shortage of gasoline, so gas station owners will hedge their bets by placing an order before the price goes even higher on Monday, thus creating a self-fulfilling prophecy of shortages on Monday because everybody panicked on Friday.
If the scare was a false one, then prices will drop or level off on Monday afternoon, creating the perception (and often the reality) of more volatility between Friday's and Mondays.
Gas Price Analysis
That was a very good analysis of how the market works and suggest it is really a very competitive market that has participants "running scared" of the competion most of the time. And Arco, for our region, is a good bellweather of how the market is headed. I do find some of the independents get out in front of the movement, whether that is because they're that close to the edge or they have more wiggle room I don't know, but they too bare watching.
And Arco, I believe, relies heavily on Alaskian sweet crude that won't last forever. As that dries up they'll fall into the fold of other majors on pricing. When will that be, when will that be?