Edmunds.com expects total US vehicle sales for the summer month of 1,533,508 new cars and trucks, which would mark a 1.1% rise from July, and a 2.5% decrease from the prior-year August.
The biggest American automaker said it sold 212,915 vehicles to retailer customers in August representing five percent drop on a year-over-year basis.
Ford said its sales rose to 28,987 vehicles in August, compared with 26,581 units during the same month a year ago, fueled by increased demand for trucks.
Nissan Motor Co. slid 6.5% to 124,638 on double-digit declines in both cars and trucks. The Japanese auto maker's vehicle sales fell 12%, offsetting a 2.7% rise in truck sales.
Total Chevrolet deliveries in August fell 3.9% year over year to 175,965 units and retail sales fell 2.7% to 142,656 units.
John Roth, vice president, sales, service and marketing for GM Canada said, "While August was a slower vehicle sales month across Canada, we demonstrated industry leadership and remain focused on product excellence and our strong retail strategy across our brands".
In late July, Ford was the first major automaker to confirm the lofty sales gains achieved since 2010 were at an end, even though they are still about 65 percent higher than the lowest sales year in 2009.
Low gasoline prices continued to drive strong demand for pricier pickups and sport-utility vehicles in August, with light-truck sales accounting for almost 60% of the industry's monthly retail sales tally.
Cars took the most serious beating in August as buyers continued to flock to SUVs.
Sales of the No. 1 selling model in the United States, the Ford F-Series pickup truck, fell 6 percent, but Ford said retail sales for the trucks were robust. Ford reported a whopping 27 percent decline in vehicle sales, reflecting buyers' overwhelming preference for SUVs.
Ford Motor Co. said its Ford brand sales were down 9 percent while its Lincoln brand sales rose 7 percent thanks to its new MKX SUV.
GM's Chevrolet line of vehicles was the carmaker's best-seller, increasing its U.S. market share by 0.4%.
Honda Motor Co 7267.T was down 3.8 percent as Accord sales tumbled 26 percent.
The company's Buick brand saw a year-over-year total sales decrease of 2.7% in July and a decrease of 12.4% in retail sales. Sales of Hyundai's bestseller, the Elantra small vehicle, were down 7 per cent, but sales of its Santa Fe SUV jumped 35 per cent.