New-vehicle sales in Mexico fell 33.5 percent in July compared with a year earlier to 56,445 units. It was the 12th consecutive month of sliding sales.
The decline has remained in the 30 percent range for four months in a row. For the first seven months of the year, sales were off 31.1 percent to 412,739.
Nissan Motor Co. and Volkswagen AG moved up one notch in the rankings of automakers' sales compared with the year-earlier rankings. General Motors Co. and Ford Motor Co. slipped one notch.
Nissan was the top-selling carmaker in Mexico in July despite a 26.3 percent drop in its sales to 12,821. That moved it ahead of GM, which had been No. 1 in July 2008. GM's sales this July tumbled 44.2 percent to 9,950.
VW moved past Ford to become No. 3. VW's sales slid 14.6 percent to 9,150. Ford's sales slumped 39.3 percent to 6,590.
Nissan also is the top automaker through the first seven months of 2009 with sales of 81,314 to GM's 74,465.
Rounding out the top six carmakers were Chrysler, down 40.3 percent to 5,882; and Toyota Motor Corp., off 24.8 percent to 3,895.