DETROIT - U.S. car buyers are tapping the brakes.
May is usually one of the strongest months of the year for the U.S. auto industry, as Americans buy cars ahead of summer road trips. But last month, U.S. auto sales were expected to drop 7 percent to 1.5 million cars and trucks, according to car shopping site Kelley Blue Book. That's the biggest monthly sales decline since the Cash for Clunkers hangover in August 2010.
Most major automakers reported lower sales in May compared to the same month a year ago. General Motors' sales fell 18 percent, Ford's were down 6 percent and Toyota's sales dropped 10 percent. Volkswagen's sales were down 17 percent. Honda's sales dropped 5 percent and Nissan's fell 1 percent.
Fiat Chrysler and Subaru bucked the trend, with sales up 1 percent each.
The declines could be a sign that U.S. auto sales are finally reaching a plateau after six straight years of growth -- a streak not seen since the 1920s. Sales rose 6 percent between 2014 and 2015 but are only up around 1 percent so far this year, and KBB expects them to remain flat this summer.
Flattening sales could be good for consumers, at least in the short term. Automakers are offering more discounts in order to keep growing their U.S. market share. Car-buying site TrueCar.com estimated that incentive spending rose 7 percent in May to average of $3,034 per vehicle.
But those discounts can hurt resale values and automakers' profits, so companies have to be careful as they deal with a dip in demand.
GM and Ford shares both fell 3 percent in afternoon trading Wednesday, reflecting investors' fears that the companies can no longer count on easy U.S. sales increases. GM's shares dropped to $30.37 while Ford's shares fell to $13.09.
Results from early in May were enough for LMC Automotive, a forecasting firm, to lower its forecast for the full year. LMC said it now expects total U.S. sales of 17.7 million vehicles this year, down from its previous target of 17.8 million.
But even 17.7 million vehicles would break the record of 17.5 million that was set last year. So even if sales plateau, they remain at very high levels.
"The sky is not falling," said Michelle Krebs, a senior analyst with Autotrader.com. "Sales remain at very lofty levels."
This May also had one less weekend than last May, which could account for some of the decline. Ford said sales were strong over Memorial Day weekend.
General Motors Co.'s sales dropped 18 percent from last May to 240,450 vehicles. Its Chevrolet and Buick brands saw the biggest declines; sales of the Chevrolet Silverado pickup, its best-seller, were down 13 percent. GM blamed tight supplies of new products, including the Chevrolet Cruze small car, as well as planned reductions in sales to rental car fleets. GM's rental car sales were down 49 percent.
Ford Motor Co. said its F-Series pickup sales rose 9 percent and its luxury Lincoln brand saw a 7-percent sales increase. But that couldn't make up for a 26-percent decline in car sales. Ford's SUV sales were flat. Ford's overall sales dropped 6 percent to 235,997.
Toyota Motor Corp. said its U.S. sales fell 10 percent to 219,339. Its car sales dropped 16 percent while its SUV and truck sales fell 2.5 percent. Sales of the Prius hybrid plummeted 36 percent, the victim of low gas prices.
Honda Motor Co. said its sales fell 5 percent to 147,108 vehicles. Honda brand sales fell just 3 percent, and the HR-V subcompact SUV saw a 15-percent sales gain. But sales at Honda's luxury Acura division dropped 20 percent.
Nissan Motor Co.'s sales fell 1 percent to 133,496. Sales of Nissan and Infiniti trucks and SUVs rose 6 percent, but car sales fell.
Volkswagen brand sales dropped 17 percent to 28,779 as the fallout continues from the German automaker's diesel emissions.
Fiat Chrysler and Subaru saw gains thanks to their reliance on SUVs, which are in high demand thanks to low gas prices.
Fiat Chrysler's sales rose 1 percent to just over 204,000 vehicles, its best May in 11 years. The all-SUV Jeep brand led the way with sales up 14 percent. But Chrysler brand sales fell 19 percent as car sales faltered, and the Dodge brand dropped 5 percent. Ram pickup sales fell 3 percent.
Subaru's sales also rose 1 percent to 50,083, a record May for the company. Sales of its best-seller, the Forester SUV, were up 1 percent.