OVER THE PAST dozen years Americans have been adjusting to the reality of expensive oil, a process that has been remarkably efficient and successful. The crises and shortages of 1974 and 1979 stick sharply in everyone's mind, while the responses to them have been gradual and undramatic. But they deserve your careful attention.

In 1973, when oil prices first began to soar, a lot of people believed that the link between energy consumption and economic growth was absolutely rigid. If energy consumption were held down by shortages, they argued, economic growth would similarly be held down. It has been evident for some time that those people were wrong, and each succeeding year has demonstrated further flexibility in that crucial ratio of energy to economic output.

Everyone has learned to be more careful, but industrial managers in particular have proved themselves to be extraordinarily inventive in extracting more performance from less fuel. This country's gross national product has risen by a third since 1973, but the country is using slightly less energy from all sources than it did then. The current savings in fuel, compared with the 1973 consumption rate, is the equivalent of $100 billion worth of oil every year -- an amount equal to this country's total oil production.

Oil prices are now falling because the world has more oil than it needs. One crucial reason for that is conservation, not only in the United States but around the world. The industrial democracies, taken together, are now using 10 percent less oil than in 1973, while their economic output has risen 30 percent. A dozen years ago flexibility on that scale did not seem possible -- least of all to OPEC, some of whose members briefly thought that they could put prices wherever they pleased.

In this country, ol imports are now hardly more than half the volume of the late 1970s because there has been a tremendous shift among sources of energy. Oil and natural gas consumption are down. Coal is up hugely, followed by nuclear power.

The result, here in the United States as in most oil-importing countries, is an economy that is much more efficient than it was in the early 1970s and much less vulnerable to being whipsawed by the instability of foreign markets. But it's worth remembering that those foreign markets are no more stable today than they were then. If falling prices of oil tempt Americans to slide back into careless pre- 1973 habits, imports will rise rapidly and the power to control prices will swing back into the hands of the producers. Oil is now a buyer's market. For the United States and for the world, it is best kept that way.