American motorists are displaying what appears to be a split personality, pumping their own gas to save money, yet demanding larger, higher-powered cars that, in turn, use more fuel.
Even in cold weather, fog, rain, and snow, millions of Americans now fill the gas tanks of their cars themselves, despite a sharp decline in fuel prices over the last year and the cold fingers that such a wintertime exercise assures.
''It seems Americans have become accustomed to do-it-yourself fill-ups, and this may be one more permanent effect of the energy situation on the consumer market,'' according to J.D. Power & Associates, a California-based marketing information firm.
In June 1979, in the midst of the second gasoline crunch to hit the United States in less than six years, some 62 percent of all male drivers - 54 percent of the total driving-age population - did the fill-up job themselves. By November, the number had fallen below 60 percent, but then began a multi-year rise that continues today. Now some 73 percent of all male automobile drivers reach for the gas hose. Among women, the figure is about 60 percent.
''As competition among gasoline retailers returns, the trend may reverse,'' the Power organization suggests. Yet so many motorists today fill up their own tank, the future is far from certain.
A negative effect of the switch to fill-it-yourself stations is the impact on the condition of the cars themselves. Many motorists who fill their own gas tank too often neglect to check the oil level of the engine or inspect the belts and hoses for wear, and they rarely give a second look at the tires unless they have a flat.
This neglect distresses automakers, who urge motorists to pay more attention to the mechanical condition of their cars. It may pay to save a nickel or more a gallon when you fill up the tank, but the saving can be of little comfort if the car runs out of oil.
And where are people spending their hard-saved fuel dollars? Ironically, at the gas pump.
Sales trends show that Americans have lost their enthusiasm for small, fuel-saving cars, opting instead for larger, higher-performance models that use more fuel. Motorists ignored the General Motors subcompact J-car when it was first introduced because of an underpowered engine. GM has since corrected the fault with spirited performance in its engine lines.
Carmakers are offering more and more turbos in their model lineups, while high-powered cars, such as the Ford Mustang SVO, are winning buyers by the busload. The trend to larger cars and performance is so pronounced that GM and Ford Motor Company won't meet the fuel-economy requirements for 1984-model cars as spelled out by the federal government.