Fiat Chrysler is lucky to be selling pickup trucks and SUVs
In fact, the only member of the Detroit Big Three to post a gain was Fiat Chrysler Automobiles, which logged an increase of 1%.
At GM, sales dropped 18%, and at Ford they slipped 6%. The steepness of GM's drop is partly explained by the pullback in so-called fleet sales to rental agencies and companies. It's focusing instead on more profitable retail sales.
But FCA's outperformance comes down to one fairly simple thing: People are still buying pickup trucks and SUVs, two segments in which the carmaker is strong. Thanks to cheap gas, easy credit, and pent-up demand, these vehicles are continuing to sell even as passenger-car sales weaken.
In fact, FCA CEO Sergio Marchionne has opined this year that a permanent structural shift is underway in the US, and that SUVs are in the process of displacing cars as Americans' vehicles of choice.
But the flip side of this is that if FCA weren't selling trucks and SUVs - and if it didn't have the Jeep brand - then it would be in a bad position.
This is why Marchionne isn't sitting on his hands but is actively trying to get FCA partnered or merged with another automaker ahead of an inevitable cyclical downturn.
But FCA was able to maintain sales momentum in May, which had two fewer selling days than a year ago.
The loss of selling days clearly hurt other automakers.
"With new-car demand stabilizing in recent months, we're left with a market that is far more dependent on sales days within a given month," said Kelley Blue Book senior analyst Karl Brauer in a statement.
"Months with as many or more sales days versus last year will likely see the same or slightly higher volume in 2016," he added. "Given the record numbers we experienced in 2015, and the continued projection for 17-plus million sales this year, the industry remains in a very good place."
FCA shares traded down 2% on Wednesday, to $7. Ford and GM dropped by closer to 3%.