THE rise and fall of gasoline prices this year has been dramatic. As 2012 began we were looking at $4.62 per gallon for regular, but by March the price had gone up to $4.97 – nearly five bucks! Then as we moved into summer the price happily started going down. By the end of June we were at $4.27 and feeling pretty good.

But then the worldwide price of oil started going back up again, so much so that we’ve had several substantial increases in what we pay at the pump in July and this month. We sort of knew it couldn’t last.

The latest increase, $.20 a gallon to $4.88 for regular, was imposed by Mobil Tuesday evening, and by the time we went to print last night the other brands, Shell and 76, had matched the increase.

Did we say $4.88? That’s technically not quite correct. Regular unleaded gasoline is now priced at $4.87.9 cents a gallon. Those fractions of a penny are apparently important, because every single service station on the island posts exactly the same figure.

The explanation is pretty simple. There is only one importer of gasoline here, and that’s Mobil. Shell and 76 buy their gas from Mobil. Sure, they add proprietary additives and market their fuel as somehow “different,” but nobody is fooled, it’s all the same.

Any suggestion that the three brands “compete” is tossed into a cocked hat by the precise, tenth-of-a-cent prices that are posted. It’s annoying, actually, the way the gasoline brands do a little Kabuki Dance every time the price changes. One of them will lead the way, and the other two invariably follow – precisely – what their supposed competitor charges.

It seems like ancient history now, but there actually were slight differences in the price of gasoline between stations. Not a big difference, but a penny or two, at least. Now we don’t even have a tenth-of-a-cent variation. Whatever happened to the old Sherman Anti-Trust Act?

The managers of the fuel companies go to some lengths to avoid the appearance of collusion in this gas price game. We’ve been told they won’t be seen in public together, at lunch or whatever, just to make sure nobody spots them and starts to talk.

Of course we talk anyway. The price of gas for our cars is a fundamental expense. Lacking an efficient or reliable mass transit system, we need our cars for pretty much everything, from getting to and from work, to taking the kids to their activities, or just to go to the store for groceries. The island is designed like the California suburbs, laid out in such a way that it is virtually impossible to live here without a car.

When the inevitable $5 a gallon finally arrives, we’ll just grin and pay it, as we always do.