DETROIT ( TheStreet) -- GM ( GM) said sales in August rose 15%, while Ford ( F) and Chrysler both reported 12% gains, as auto sales continued to gain ground. Chrysler said overall August sales numbers translate to a seasonally adjusted annual sales rate of 16.1 million vehicles. Ford said industry sales gained about 17% in August. Ford said its retail sales grew 20%, for the best monthly retail performance since 2006, even as tight inventories crimped sales in several key segments. GM said its retail sales gained 22% while fleet sales fell 8%. Ford announced 2013 fourth-quarter production of 785,000 vehicles, up 7% from 2012. "The second half of 2013 is off to a very solid start for GM and our model-year change over and new product launches are going smoothly," said Kurt McNeil, GM vice president, U.S. sales operations, in a prepared statement. "We have a lot of momentum and we feel good about the direction of the U.S. economy as we prepare to launch even more new products," Every GM brand reported double-digit sales gains, with Cadillac up 38%, Buick up 37%, GMC up 14% and Chevrolet up 10%. Deliveries to retail customers were up 38% at Cadillac, 22% at Chevrolet, 16% at GMC and 24% at Buick. Cadillac's retail sales were the brand's best August since 1989. Ford said F-Series sales topped 70% for the second time this year. The last time F-Series had sales of more than 70,000 vehicles in two separate months in a calendar year was 2006. Fusion sales rose 22% to 71,115. Ford small-car sales rose 30% to 30,148. Fusion sales totaled 24,653, the best August sales ever, with the strongest growth in the West, where Fusion retail sales gained 63%. "Producing more Fusions at Flat Rock Assembly with its 1,400 new workers is a welcome opportunity, as Fusion showed great strength in August," said Ken Czubay, Ford vice president, U.S. marketing, sales and service, in a prepared statement. "Small cars and hybrids continue to outpace the market in the coastal regions of the U.S., with Ford brand retail small car sales growing at more than three times the rate of the U.S. small car industry," Czubay said.