THE CURRENT auto fuel-efficiency standards expire in 1985, when each manufacturer's new cars must have an average mileage of 27.5 mpg -- less than most imports get today. Because of the long lead times needed by the industry, the question that has to be answered now is what should happen after 1985 -- should the standards be abandoned, or should they be raised? The debate began this week with hearings before Congress on a bill that would raise the average to 40 mpg by 1995.

There is little disagreement that the existing standards have been a crucial factor in saving the auto industry from even greater financial distress than it is now suffering. Clearly, though, it has not been enough. Total automobile sales were down by 20 percent in March, yet imports had their third best month ever. Nevertheless, the four domestic auto makers vehemently oppose any standards for the period after 1985. Why?

The reasons presented this week were little more than a repetition of the same arguments that were made against the current standards when they were being debated in 1975. The only difference was that this time there was general agreement that the 40-mpg goal can be met. In fact, the Department of Energy believes that 43 mpg to 50 mpg is technically feasible, and the only technical analysis presented to the committee concluded that 84 mpg (yes, you read that right) could be achieved.

In the face of the evidence, the representative of Ford Motor Co. argued that "there is no longer a need to play catch up" with imports. The company is committed to improving mileage, he said, but new standards would render obsolete facilities that are only now being built. General Motors took a different tack, arguing that it has been ahead of the market all along and that "if anything should be said, it is that our efforts have been handicapped by public policies that have falsely portrayed the real cost of fuel." In other words, the industry's problems are the government's fault. Coming from an industry that regularly lobbies against higher gasoline prices because of their effect on car sales, that argument was a little too much for some of the senators' composure.

The most popular argument, of course, was that not enough is known about the future to allow any decision to be made now. But at least one central fact is known beyond any doubt: oil resources are declining, and imports are robbing the country of too much of its wealth and freedom of action. The responsible conclusion is that over the next several decades the nation's well-being depends on its exploiting every opportunity to reduce its need for imported oil -- including conservation and increased production of alternative energy sources.

While Detroit might produce fleets averaging 40 or 50 mpg without standards, it also might not. Certainly, past experience and current performance justify some skepticism on that score. The point is that if in the year 2000 new standards turn out to have been unnecessary, little or nothing will have been lost. But if, on the other hand, they prove to have been needed, the cost of not having had them will have been enormous. The only real questions, then, are how high to set the post-1985 standards -- 40 mpg seems to be too low -- and whether the industry will need financial help of some sort to meet them.