Dave Strom of South Boston, Va., recently bought a tiny Smart ForTwo Passion Coupe, made by Daimler, the German automaker.
Mr. Strom also owns a pickup truck, which he uses mainly to haul his boat. When he runs errands, he drives his Smart, which he says is getting 45 miles a gallon.
“I had to smile the other day when I filled my tank for $18 and the guy next to me had a Ford Explorer and the pump was clicking past $80,” said Mr. Strom, a 66-year-old retired manager of a Chevrolet dealership.
Previous spikes in sales of smaller cars were often a result of consumers trading down during tough economic conditions or gas-price increases. When the economy improved or fuel prices dropped again — as they did after the oil-price shocks in the 1970s eased — buyers invariably went back to bigger vehicles.
But with oil prices expected to remain high for years, auto industry executives are seeing a turning point.
“The era of the truck-based large S.U.V.’s is over,” said Michael Jackson, chief executive of AutoNation, the nation’s largest auto retailer.
Sales of traditional S.U.V.’s are down more than 25 percent this year. In April, for example, sales of G.M.’s Chevrolet Tahoe fell 35 percent.
Full-size pickup sales have fallen more than 15 percent this year, with Ford’s industry-leading F-Series pickup dropping 27 percent in April alone. Sales of pickups, though, are expected to strengthen with the economy, because of their use as commercial vehicles.
The rise in sales of more fuel-efficient vehicles occurred during one of the industry’s worst months in more than a decade. For the month, G.M. sales dropped 23 percent and Ford slid 19 percent, while Toyota fell by 5 percent. The figures were adjusted for the fact that this April had two more selling days than a year ago.
Another bright spot in the numbers were sales of so-called small crossovers — which look like little S.U.V.’s and are based on car underpinnings.
Like small cars, they also accounted for about 20 percent of the total industry sales for the month, according to the research firm J. D. Power & Associates.
The analysis by J. D. Power also showed that 42 percent of all vehicles sold in April were equipped with four-cylinder engines, compared with 38 percent for six-cylinder engines.
How the downsizing of America’s vehicle fleet will affect fuel consumption is still largely unknown. When gas prices rise, as they are now, many drivers simply drive less to save money.
But there are some indications that the trend toward smaller vehicles will reduce the nation’s fuel use. In California, motorists bought 4 percent less gasoline in January than they did the year before, a drop of more than 58 million gallons, according to the Oil Price Information Service.
“That is an incredible year-over-year drop,” said Tom Kloza, the organization’s chief oil analyst. “Some of it clearly has to do with changes in the vehicle fleet.”