New-vehicle sales in Mexico fell 32 percent in August from a year earlier to 58,927 units.
It was the fifth straight monthly decline in the 30 percent range. For the first eight months of the year, sales dropped 31 percent to 471,666.
Nissan Motor Co. continued to pull ahead of its rivals in Mexico, while the Detroit 3 lost ground.
Nissan was the No. 1 automaker in Mexico in August, up from No. 2 a year earlier. Its sales slid 26 percent to 12,539.
Volkswagen AG was No. 2, up from No. 4 a year earlier. VW's sales slipped 15 percent to 9,981.
General Motors Co. was No. 3, down from No. 1. GM's sales tumbled 47 percent to 9,243.
Sales at No. 4 Ford Motor Co. dropped 31 percent to 9,112.
Chrysler Group's sales dropped 33 percent to 6,637.
Among the top 10 automakers in Mexican sales, Honda Motor Co. had the worst August. No. 7 Honda's sales plunged 59 percent to 1,867.
No. 9 Renault SA had the best August in percentage terms; its sales slipped 12 percent to 1,127.