This month's US new vehicle sales are expected to be around 1.17m units, almost 6% down from August 2008 but up about 18% from July 2009, according to Edmunds.com.

Edmunds' analysts have predicted that August's Seasonally Adjusted Annualised Rate (SAAR) could be just over 13m, this year's highest by far. However, a week-by-week analysis reveals that this summer has been the industry's most volatile period in history, due to the government's Car Allowance Rebate System (CARS), otherwise known as 'cash for clunkers'.

"Cash for clunkers sent the sales rate on a wild roller coaster ride," said senior analyst Jessica Caldwell. "The SAAR surpassed 19m in late July, bounced around in the 15m range early in August and has fallen to around 8m currently. Ending August on such a low note does not bode well for September."

Analysts noted that the unusual inventory shortage faced by many dealerships could mean that deals are stuck in the pipeline and, when accounted for, will move the numbers significantly.

August 2009 had 26 selling days, one less than last August 2008.

"Hyundai and Ford were the biggest winners in the cash for clunkers contest, experiencing significant growth in August sales compared with a year ago," said senior analyst Michelle Krebs. "This is likely to be a record month for Hyundai, beating their prior sales record by a mile - maybe as much as 40%."

"In contrast, some automakers couldn't really make clunkers work for them, and their August sales suffered as a result," Krebs added. "Chrysler and GM - both hurt by extended factory shutdowns during their Chapter 11 proceedings - had limited inventory to feed cash for clunkers, while high-end automakers didn't have the right products for these buyers."

Edmunds estimated the combined monthly US market share for Chrysler, Ford and GM domestic brands at 42.2% in August 2009, down from 45.7% a year ago and down from 44.2% last month.

Chrysler sales are seen down 22% year on year to 86,000, Ford up 22% at 185,000 and GM down 28% to 222,000 units.

Amongst major import brands, Edmunds.com predicts Honda will sell 137,000 units in August 2009, down 7% year on year, Hyundai will be up 63% to 108,000, Nissan down 18% to 89,000 and Toyota off 1% to 209,000 units.