AMERICANS CAN properly congratulate themselves on the speed and perseverance with which this country is cutting down its consumption of oil and gasoline. But it's worth noting that Western Europe and Japan are cutting down much faster.The habit of plenty is not so deeply engrained there, and the sense of vulnerability is sharper. Motorists accept the necessity for fierce taxes on gasoline because, perhaps, they know that the world sometimes deals harshly with countries that don't react quickly to danger.

In this country, oil consumption has been dropping steadily at a rate of about 8 percent below a year earlier. In Japan and Germany, by late last year, it was dropping at a rate of about 15 percent below a year earlier. This steady decline in the demand for oil is the only really reliable way by which the industrial nations can protect themselves from further disruptions and damaging price increases.

While the reductions in the use of oil promise eventually to diminish some of the risks, recent changes in the international oil trade are increasing others. As recently as the early 1970s, a small number of gigantic companies bought, sold and transported nearly all of the oil moving from one country to another. The defects of that system are well known; its virtues have been less adequately advertised. The big oil companies were effective buffers between governments and provided a high degree of flexibility in the movement of oil. When the Arab governments tried to embargo the United States in 1973-74, the oil companies merely switched shipments around to maintain deliveries without technically violating the Arabs' prohibitions. Today the OPEC countries sell most of their oil through their own government agencies. Increasingly, they sell directly to other governments. By one expert estimate, about one-sixth of the oil shipped to the industrial countries is now handled through government-to-government sales. That proportion is rapidly rising.

The importing countries go into these deals in the hope of insulating themselves from future turmoil. But the further this trend goes, the less latitude each buyer will enjoy in an emergency -- and the more leverage each seller will be able to exercise. Perhaps this trend is inevitable, as the exporting countries learn to develop and exploit the political power that oil carries. That's only one more reason -- and a peculiarly urgent one -- for the industrial countries to press ahead, rapidly and relentlessly, with oil conservation.