Orange County automakers’ sales were again mixed in August, even as the monthly national sales total surged nearly 20%.

Automakers nationally sold a collective 1.29 million vehicles during the month, putting the annualized national selling rate at 14.52 million vehicles, the highest it has been all year, according to Woodcliff Lake, N.J.-based Autodata Corp.’s online industry researcher Motor Intelligence.

Irvine-based Kia Motors America Inc. saw the largest percentage increase of local automakers during the month, with sales up 21.5% from a year earlier to 50,028 vehicles.

Kia, part of South Korea-based Hyundai Kia Automotive Group, is “significantly ahead of last year’s all-time annual sales record pace,” the company said in a statement.

Kia sold 485,492 vehicles in 2011. The automaker has sold 386,809 vehicles so far this year.

Hyundai Motor America Inc., with temporary headquarters in Costa Mesa while a new headquarters in Fountain Valley is under construction, saw August sales rise 4% from a year earlier to 61,099 vehicles.

Sales for Cypress-based Mitsubishi Motors North America were off 46.8% from a year earlier to 4,249 vehicles.

Brea-based American Suzuki Motor Corp. reported August sales down 18.3% to 1,968 vehicles.

Mazda North American Operations in Irvine sold 22,234 vehicles last month, down 1.8% from a year earlier.

Anaheim-based luxury hybrid automaker Fisker Automotive Inc. does not break out monthly sales.