THE AUTOMOBILE market has now swung back toward the big models - with the usual unhappy implications for future oil imports. The companies are now making a wide range of small cars, but the customers are edging back toward the big ones that they're used to. Next fall the industry comes under a legal requirement to get its average fuel efficiency up to 18 miles a gallon, and even higher in the years beyond. But that average is calculated according they can push the manufacturers under the limit and to sales. If the customers keep going for the big cars, subject them to stiff federal fines. The companies spent half a century telling people that "Big is Beautiful." Habits and preferences don't change overnight.

You might have noticed that General Motors plan to shut down its Lordstown, Ohio, plant this weel until inventories of the Vega are worked down. It hasn't been a good year for the little Vega. By this time last year, GM had produced 44,000 of them; so far this year it has made only 8,000 and has more unsold ones on its hands than it wants. As for the even smaller Chevette, it had made 45,000 of them by this time last year; so far the 1977 production is just under 18,000. But for GM as a whole, production is up a rich 8 per cent over last year. The increase is all in the bigger cars. It had made 64,000 of the standard Chevrolet by this time last year, but 99,000 of them this year. When the model year opened last fall, GM expected to sell enough small cars to send its average mileage up to 18.4 miles per gallon. But now it expects the average to fall around 17.8 miles.

It's much the same story across the street at Ford. The company's overall production is up 11 per cent over last year, but both of its smallest models, the Pinto and the Maverick, are running at half of last year's level. Ford had hoped to reach an average mileage of 17.1 miles per gallon for its total sales this year, but it too is now revising the forecast downward.

Ford considers this year to be a dress rehearsal for 1978 and the new federal rules, and it is now beginning to force the market a bit. Last month it announced a price cut on the small cars, and price increases on cars with the big V-8 engines. It also nudged the cost of air conditioners up just a little. Among some of the big cars, it's now offering lighter engines at lower prices. Ford's vice president for sales. Bennett Bidwell, predicted the other day that there will be increasing use of that kind of differential to persuade customers to take a closer look at the small models.

Even with the disappointing sales of the small cars, there have been remarkable improvements in gasoline mileage over the past several years. You might remember that the industry brought out the least efficient line of cars in its history in the autumn of 1973- just in time for the big jump in oil prices and the Arab embargo. GM's cars that year averaged about 12 miles to the gallon. By next fall, the industry as a whole will have achieved an improvement approaching 50 per cent, partly through lighter designs, partly through better air pollution-control technology. By 1985, the law will require another improvement of the same magnitude, to 27.5 miles per gallon.

Consumers began moving rapidly toward smaller cars after 1973, but then the movement lost momentum.What will it take to get the market back on the right track? The companies' pricing policies will have a great deal to do with it. So will public policy. Over the past couple of years, neither Congress nor the administration has been very candid with Americans about the coming squeezes on oil supplies. That defect will be remedied, we trust, when President Carter announces his energy program next month.