DETROIT: The nation's automakers are bracing for quieter showrooms and slower sales this autumn after the Cash for Clunkers program offered a big but unsustainable boost in August.

US sales of cars and light trucks rose to 1.3 million in August, a roughly 30 percent increase from July. It also was the first monthly year-over-year gain since October 2007.

Ford, Toyota, Hyundai and Honda were the big winners as consumers snapped up their fuel-efficient cars. Rivals Chrysler Group LLC and General Motors Co endured another month of falling sales, although their high-mileage vehicles did better.