Fleet sales for the seven best-selling automakers in the U.S. rose 2.4 percent in August while retail volume for the same seven declined 5.4 percent.
But the pace of fleet business did slow considerably last month.
Through August, the seven companies have grown fleet by a combined 8.2 percent, and it would be much higher if General Motors were taken out of the mix.
GM has cut fleet business 21 percent so far this year but was down just 4.4 percent in August compared with the same month last year.
Nissan North America, which has expanded fleet volume by 40 percent so far in 2016, was down 5.5 percent compared with August 2015.
Fiat Chrysler also cut back on fleet last month, though far less dramatically. FCA US was up 22 percent in August, which lowered its full-year increase to 32 percent.
Ford Motor Co.'s fleet business is up 13 percent for the year but declined 9.5 percent in August.
"Our rental business was very frontloaded to the first half of the year and then balances out the rest of the year," said Ford sales boss Mark LaNeve.
"This was one of the months where we had a decline in the rental business, as planned."
Toyota Motor was an outlier last month. The group's fleet sales rose 11 percent in August but for the year were down 3.7 percent.