I HAVE JUST ORDERED a 1984 GMC Suburban. This is a station wagon built on a light-truck chassis. Mine will be a little more than 18 feet long and weigh more than 4,700 pounds.

I'm not sure what came over me. I've been a small-car booster/owner since 1953, and now, suddenly, I have ordered a vehicle large enough to require a commercial operator's permit.

It has nothing to do with any fancied gasoline glut. I know there is less petroleum in the ground now than there was when Schlesinger and Carter gave us Energy Crisis 2. It has nothing to do with interest rates. My tax guy begs me to borrow money. He believes that usurious rates are philanthropic.

I think the real reason I'm buying this behemoth is to celebrate the end of the recent recession, to hail Mrs. Thatcher's victory in the British elections and to perform an automotive act that is socially irredeemable without being illegal. It is exactly the boat in which I'd like to ride the rising tide.

Thinking about it fills me with shivers of anticipation. There will be seats for me and Mrs. Davis, plus a string quartet, with instruments, and any son or daughter who is not embarrassed to be seen with us. It will have front and rear air conditioners. It will have electric windows and central door locking. It will feature the optional stereo system with tape deck, which is condiderably better than the one in my house. It will be equipped with a trailer hitch, despite the fact that I have absolutely no intention of towing a trailer. A vehicle like my new Suburban would look, you know, wimpy, without a trailer hitch.

I've ordered the full rock-group tint on the rear windows, both to conceal my goods and chattels from the public gaze and to keep the sun's rays off the two golden retrievers and the Brittany spaniel who'll be riding back there. Because I want big tires and strong suspension, I have ordered the three-quarter-ton version, as opposed to the less robust half-ton model. This will allow me to carry an extra quarter-ton of those odds and ends one hates to leave at home, and will give me an extra inch of ground clearance. We want to give it a name, but we can't decide between Wretched Excess and Manifest Destiny.

I am not alone in this apparent loss of my finer automotive sensibilities. Thousands of Americans -- currently a little less than 14 percent of the current car market -- have decided that the room, ride and safety they perceive to be the big car's main selling points outweigh any parsimonious considerations of fuel economy or lower purchase price.

There's another reason. Many of us want to buy American cars -- some for patriotic (or jingoistic) reasons, some for economic reasons, some for reasons that are purely nostalgic -- and it doesn't take much shopping to realize that the big car is still the car that America builds best. It's also the car that neither Europe nor Japan has shown very much interest in building . . . so far.

Too often, American small cars look as though they're ashamed of themselves. A Toyota Tercel wears a jaunty expression of self-worth. A Chevrolet Chevette looks like the Baptist minister's car, caught in a motel parking lot. There is absolutely nothing wrong with a Chevette, mind you, except that it obviously would give anything to be two feet longer and about a thousand pounds heavier. No, America has not yet convinced itself that it is small car country, and our home-grown small cars reflect that doubt.

If one resides in the vast, pleasant chunk of Eisenhower's America that still exists between the two coasts, there's very little reason to believe that small cars are the wave of the future. The roads are long and straight, and the distances involved in one's daily routine are apt to be great.

People in the heartland certainly don't seem to be getting any smaller, so the traditional big-car buyer might be forgiven for questioning the logic in a massive shift to Japanese-style small cars. The 4,000-pound American sedan with its V-8 engine and automatic transmission was, until quite recently, the envy of the entire world, civilized and uncivilized alike, and it still makes a lot of sense for people who don't often associate with bicoastal trendies.

We are not outlaws. I should say, they are not outlaws. (They would probably regard me as some kind of gleeful, mad-dog automotive hedonist, bent on giving big cars a bad name.) They are the honest burghers of Middle America. They fought in World War II. And Korea. Uncles and fathers who never doubted that their postwar lives would be one big American car after another. They are not tempted by small cars, never have been. They buy their big cars for reasons that are, to them, solid and sensible, unarguable.

There is nothing new about their prefrerence for large cars. They once represented the overwhelmimg majority of American car buyers, but in the late 1950s imported cars began to make permanent changes in America's automotive preferences. The younger, more affluent, better-educated automotive consumers, warm to the touch and enthusiastically in favor of change, became small-car partisans. The older, more conservative automotive traditionalists began to circle their wagons. More of those young, enthusiastic change-seekers have come into the market every year, while the old traditionalists' numbers are dwindling. As they go, so goes the market for large cars in America.

Interestingly enough, management in the domestic automobile industry is dominated by exactly this dwindling demographic and psychographic slice of the population. They share the fears and doubts of that broader group, and they too have circled their wagons.

Life is not a bed of roses for the domestic automobile manufacturers theseedays. As heartened as they must feel by the return of consumer confidence, as pleased as they surely are when we vote with our payment books for the larger cars that are most profitable for them to build, there comes a point where our lust for room, ride, comfort and safety puts them on the wrong side of the law. Back in the '70s, when our legislators yearned to demonstrate that they were just as antiestablishment and antitechnology as any of the other disorderly mobs that had lent so much color to the national fabric during the previous decade, they created something called CAFE.

CAFE stands for Corporate Average Fuel Economy, and it is only one of thousands of regulations laid across the back of our domestic automobile industry during a time when it seemed to Washington to be so durably successful that it deserved some confiscatory punishment. CAFE forced American car manufacturers to meet an escalating set of fuel economy standards or pay heavy penalties. (This year alone, GM could be assessed penalties up to $420 million, Ford up to $110 million.)

The legislators proudly imagined that they were forcing the industry to do something that it would have done in its own enlightened self-interest if it had only been as enlightened as the members of Congress.

As it happened, the free market was there ahead of the legislators, providing a carrot for car makers that worked better than the legislative stick. Until this year, the manufacturers and their customers saw to it that American cars consistently delivered corporate average fuel economy that ran well ahead of the standards mandated by CAFE. (These good years provided credits that U.S. manufacturers can apply against current penalities, but the accumulated credits cannot offset a long-term surge in big car sales.)

Now the free market and I have diverged from that perfect plan. As our spirits and confidence rise, some of us are buying the big cars that Congress thought it had prevented us from buying.

We should be ashamed of ourselves, but we aren't. We may bankrupt General Motors and Ford with our born-again enthusiasm for their heavyweights, but we don't care. For one thing, the cars we buy today are averaging fuel economy that is on the order of 40 percent better than it was when CAFE was mandated in 1975. For another, it is fundamental to the American character to confound the projections of elitist soothsayers.

CAFE could be abandoned this afternoon and it would make very little difference to the history of America's relationship with the automobile. We will buy our big cars today. Then, as sure as Ralph Nader sleeps with Emma Goldman's picture in the pocket of his fireproof pajamas, something awful will happen at the far end of the Mediterranean to put us back on the track toward smaller, more efficient cars.

Even without any Arab-induced oil shortage, the pump price for gasoline is again showing a steady rise, and that alone will tend to dampen demand for larger cars. Finally, the big- car constituency just keeps getting older and smaller. For whatever reason, or for all the above reaons, the curve on the chart from 1946 to the turn of the next century is inexorable. Europe, Japan and the United States are on converging small-car courses in that longer term.

We have been, and will continue, buying and driving those automotive products that make the most sense to us at the moment. But since our automobiles and our dreams seem to be traveling in the same direction for a while, many of us like the idea of being able to get the whole family and all the dreams into one vehicle.