An estimated 1,087,000 new cars will be sold in the US in August for a projected SAAR of 12.3m, said, noting the sales pace is virtually flat compared to July’s 12.2m SAAR.

“Auto sales stayed on a relatively flat road this month, even as the stock market took a roller coaster ride,” said chief economist Lacey Plache. “Stronger buying conditions are telling consumers to go ahead and make their car purchases but a weak economic landscape is telling them to wait until later this year, or even longer. This is the battle that will determine exactly how much the auto industry will grow this year.”

Overall sales are expected to be up 2.6% over July 2011 and 4.8% year on year. estimates that retail SAAR will come in at 10m in August with fleet sales accounting for 18.5% of all sales this month.

Nissan will see the biggest month-over-month gains among the top six automakers and is projected to sell 10.4% more vehicles in August than July, and 16.9% more vehicles than in July 2010. The boost in sales is expected to bring Nissan a 0.6% increase in market share.

“Nissan’s market share growth is a testament to how well it has recovered from the March earthquake compared to its chief Japanese rivals,” said senior analyst Jessica Caldwell. “In recent marketing campaigns, Nissan has been directly targeting shoppers who have trouble finding Toyota and Honda vehicles in stock, while further enticing them with juicy incentives like zero percent financing on a majority of their models.” reckons Toyota has done little in August to build on its momentum from July, with just a 1% increase in sales this month and a decrease of 0.2% in market share over the same period. Its August sales are expected to be down 14.4% compared to last year.

Even with lingering inventory issues still to sort out, Honda will likely show some month over month sales gains in this month. Edmunds projects its August sales will grow 5.4% over July, with a market share gain of 0.2%. Compared to last year, however, August sales are still expected to be off about 25%.

Ford will be the only major automaker this month to report a decline in sales from July to August. Its sales are expected to be down 0.5% from July, leading to a market share loss of 0.5 points. Ford’s sales will still enjoy a 9.7% increase over August 2010, the forecaster said.

Chrysler and General Motors are each expected to post month-over-month sales gains of 7.8% and 3.3%, respectively. Chrysler’s market share will climb 0.5% in August while General Motors ticks up 0.1 points over July.