THE FAMOUS oil glut continues. There's a slight surplus of oil on the market currently, and prices have drifted down from the peak of last February and March. Because of that decline, people don't seem to be trying quite so hard to conserve fuel. You can see it in the figures on gasoline sales. Consumption no longer seems to be declining.

That would be tolerable, perhaps, if there were any reason to think that the glut would last. But there isn't. As gluts go, it is a modest one and could vanish at any moment. There are now hints and rumors that OPEC is about to meet and try again to agree on the Saudis' prices. If the Saudis get what they want, the other half of the bargain is that they will also begin cutting their own gigantic production to keep prices from sinking any further. The bargain also seems to imply future price rises, enforced by slight but persistent shortages.

Rises coming how fast? Opinions, as always, differ. But most people who follow the subject carefully think that oil prices will continue to go up significantly faster than the general level of inflation.

The important thing is the way these rises occur-- whether they are gradual and predictable or, as in the past, erratic and destructive. The industrial world has caught itself in a deeply damaging cycle. First, oil consumption rises, stretching supplies taut. Then, a crisis --a war, or a revolution--disrupts the flow and, with a sudden shortage, prices shoot up. Appalled consumers cut back their use of oil, sharply. A small glut appears, and prices recede just a little. Consumers assume that the need to conserve has ended, and they begin sliding back toward old habits--and that's when consumption begins to rise again. The world has now been through it twice in the past eight years, and the cycle is starting again.

What does a foresighted government do to prevent it from happening a third time? As an immediate precaution, it continues to fill the Strategic Petroleum Reserve as fast as it can. There the Reagan administration is doing well. It now has more than 200 million barrels of crude oil in underground storage, the equivalent of 40 days' imports.

But beyond that, this administration doesn't seem to have much in mind. Careful policy would keep pushing the economy slowly but firmly away from oil. It would proceed at a moderate pace with more light water nuclear reactors, rather than chasing dangerous diversions like the breeder. It would take the controls off natural gas prices. Above all, it would put a stiff, and rising, tax on gasoline to take the initiative away from OPEC and the vagaries of a cyclical oil market.

That tax would provide a constant reminder to Americans to cut down on gasoline, and reduce their exposure to the next world shortage. The tax would also, by the way, raise some money for the Treasury --which, as you've probably noticed, could use it.