AMERICAN CONSUMPTION of gasoline is, ominously, beginning to increase again. While the price was going up, consumption steadily fell. That reduced oil imports, strengthened the dollar and in general was good for the economy and the country. But sometime in mid-spring the price of gasoline turned around and began, slightly, to fall. The response has been immediate.

For the first time in more than two years, since the shortages and gasoline lines of early 1979, Americans' use of gasoline is now running significantly higher than a year earlier. The nationwide average price was $1,388 per gallon in March. But two months later it had sagged to $1.370 -- just as the summer driving season began. Here in Washington metropolitan area, a survey by this newspaper showed an average price of $1.442 in late April. Two months later, on June 29, it was $1.428. If those prices are adjusted for inflation, it appears that the drop was 2 or 3 percent here and around the country. In response, gasoline use is currently up about 2 percent compared with last June.

It's simply another demonstration that this country's thirst for gasoline is sensitive to its price -- and not to much else. The evidence over the past decade is clear. Introducing more efficient cars does not, in itself, save gasoline. The great value of the shift to small cars is that it has enabled people to accommodate rapidly rising fuel prices without deep disruption of their daily lives. But, just as in the days when gasoline was cheap, a drop in prices means that people will drive more.

This country's total use of oil and its oil imports have both dropped sharply since the last crisis. That one began with the Iranian revolution and imposed on this country's first the shortages, then a great surge of inflation, then a recession. The United States still depends on imports for one-third of its oil, and is still deeply vulnerable to foreign disruption. The present drop in prices at the filling stations has only one cause -- Saudi Arabia's current oil production policy -- and that could change at any moment.

It would be unspeakably foolish to allow this temporary surplus in the world oil markets to reverse the progress here toward conservation. A competent energy policy would impose a gasoline tax to keep drivers cautious. But on the subject of energy, the administration merely smiles and puts its trust in the world market. That means, for the present, letting the Saudi government make energy policy for Americans.