The domestic auto industry listed sharply slower sales last month in yet another indication of a sluggish U.S. market.
Ford reported a 7.5 percent sales decline compared to July 2017 but attributed the bulk of the decrease to lower sales to commercial and rental customers.
General Motors and Fiat Chrysler, meanwhile, posted declines of 15.4 percent and 10 percent, respectively.
FCA also blamed the decline in part on rental fleet sales, while General Motors highlighted strong crossover sales but acknowledged that the U.S. market "continues to moderate."
Those companies' primary Japanese rivals fared better in their latest reports, but both Nissan and Honda also reported declining sales last month.
Nissan sales fell by 3.2 percent as Honda's declined by 1.2 percent. Honda, however, saw a 2 percent gain in its flagship division and among its car models.
Car sales overall have suffered in recent months as buyers instead opted for larger trucks and SUVs.
Toyota was the lone company among the top U.S. automakers to report a monthly sales increase. The jump of 3.6 percent represented Toyota's "strongest month of the year so far."
Those six companies comprised more than 75 percent of the U.S. auto market in June, according to data from The Wall Street Journal.
