CONGRESS knows that the country needs to save oil and gasoline, but it hasn't the courage to enforce conservation directly with a tax. That's why it keeps coming back to indirect -- and inefficient -- methods like federal regulations requiring manufacturers to produce high-mileage cars.

The Senate is about to take up a bill that would tell each manufacturer to raise its cars' fuel mileage by an average of 40 percent over the next decade. Enacting this bill would certainly be better than doing nothing.

But the trouble with automobile mileage laws as the country's chief instrument for saving fuel is that they encourage people to drive more. By reducing the number of gallons needed for each trip, it makes that trip cheaper. That's not just a theory. You may have noted a report in this paper a few days ago observing that air pollution in the Washington area is much higher than predicted. The reason, according to the Council of Governments, is the rapid increase in what it calls leisure driving -- a category that now constitutes two-thirds of the miles driven here. One reason for that is the falling price of gas, and the other is the drop in the gas used per mile. Driving is sensitive to fuel costs. The result is that a large increase in automobiles' gas mileage translates into only a small decline in gasoline sales.

Raising a car's gas mileage by 40 percent is expensive, but the cost gets wrapped into the price of a new car and people tend to blame it on the automobile companies. If the Senate had chosen instead to go ahead with a gasoline tax, posted visibly on every pump, those same people might have tended to blame their senators. The gas mileage bill is a fuzz-the-responsibility bill.

One inequity in it particularly needs to be remedied. It says that each manufacturer must raise its cars' average miles per gallon not by the same number of miles but by the same percentage. The companies now producing high-mileage cars would have to make large improvements, those doing less well would have to do less. That's deliberate discrimination against the Japanese.

But for all its many warts, this bill ought to be passed. Congress at least recognizes the obvious need to get the country's demand for oil under control -- in contrast to the Bush administration, which has so far evaded the subject altogether. The number of miles driven by each American car has been rising steadily, and the number of cars is rising more than twice as fast as the population.