Now might be a good time to buy a gas guzzler.

In the current gasoline squeeze, prices of big American cars have been tumbling drastically, while small, fuel-efficient cars - usually imports - have been commanding top dollar.

This is not to disparage small cars. Americans should have turned to them years ago, and they represent the future of motoring in this country. But sometimes it pays consumers to swim against the tide. This could be one of those times.

From an overall standpoint, the nation is on its way toward increased energy conservation as the gas guzzlers of a few years ago are gradually replaced with more efficient cars. But the big cars are not going to be junked overnight. Some people - usually those at the lower end of the economic scale - will continue to drive them throughout the cars' useful lives.

For a consumer willing to spend a little time calculating, they could represent a transportation bargain.

Take a few simple examples. These are from the eastern edition of the Official Used Car guide published for the National Automobile Dealers Association. "The book," as it is often called, lists average retail prices charged by dealers.

It shows these prices for several models of two domestic gas guzzlers: $925 for a 1973 Plymouth Fury III four-door sedan and $1,000 for the two-door hardtop. A 1973 Pontiac Catalina four-door lists at $900 and the hardtop version at $975.

The models have the usual equipment - that is, automatic transmission, V-8 engines, power steering and brakes, but no air conditioning.

The average for the four models is about $950.

In the same edition, the book lists these prices for similarly equipped models of several popular imports: $1,875 for a 1973 Toyota Corona four-door and $1,950 for the two-door hardtop, and $1,850 for a 1973 Datsun 610 four-door and $1,900 for the two-door hardtop.

The average for the four imported models is slightly more than $1,890. That's a difference of about $940.

To keep the example simple, assume that the domestic gas guzzlers have 20-gallon fuel tanks and get about 13 miles to the gallon.

The imports, on the other hand, have something near a 13-gallon fuel tank and get about 20 miles to the gallon.

That means that any of the cars should go about 260 miles on a tank of gasoline.

With gasoline at $1 a gallon, which is where it seems to be headed, it would cost about $20 to fill up the domestic car and about $13 to fill up the import. That's a difference of $7 a tankful.

The average motorist travels about 12,000 miles a year. At 260 miles to the tankful, it would take about 46 tanks of gasoline to drive for one year.

Multiply the number of tankfuls by the additional $7 it costs to run the gas guzzler. It works out to an added cost of $322 in one year.

But remember that the imported car originally cost $940 more than the domestic model. That means that you could drive the domestic for nearly three years before it would start to cost more money than the import.

If you drove the domestic for only two years, you'd be nearly $300 ahead.

In addition, you'd have the use of your money over that period. If you borrowed the $940 at 10 percent interest, it would cost you $94 extra the first year. And, of course, you would be buying the gasoline over the two or three years with inflated dollars instead of money at today's value, although that could be canceled out by fuel price increases.

These figures obviously vary greatly, depending on which makes and models you compare. For example, Fords and Chevrolets are worth slightly more in the used-car market than Plymouths and Pontiacs, so the difference would be less.

On the other hand, if you compared the 1973 Pontiac to a Volvo of the same year, the difference would be considerably more.

The foregoing, of course, considers only purchase price and gasoline costs. It does not include depreciation and repairs.

Imported cars, generally speaking, depreciate more slowly than domestic cars, so are worth more in the end. On the other hand, parts and repairs on foreign cars often cost more.

Moreover, when cars get into the 8- and 9-year-old category, their selling price usually depends more on condition than make or model. It is conceivable that the domestic gas guzzlers could rebound in value. It has happened before.

During the Arab oil embargo, when gasoline was in short supply and prices soared, the gas guzzlers dropped in value - just as they have recently. But after gasoline became readily available again, and consumers became used to the higher prices, the demand for big cars resumed.

The current fuel shortages, say the government and the oil companies, are likely to become chronic. But the shortage now is only on the order of 5 to 10 percent, which can be handled with a bit of judicious conservation.

It is unlikely that the nation will tolerate lines at service stations for very long. And even where there are lines, a motorist who makes it to the pump can usually have his tank filled - regardless of whether it holds 13 or 20 gallons.

There obviously are many variables in all this. Some people have no need or desire for a big car. But the sales statistics show that, given the choice, most Americans do like the room and comfort of the traditional gas guzzler. What it amounts to is some comparison-shopping, which consumers are doing in increasing numbers.

After a little time with the classified ads, you could decide there is a gas guzzler in your future.