There were plenty of positive numbers in September’s sales reports. U.S. auto makers sold 1,049,754 light vehicles in the month, a 9.8% increase over year-ago that pushed the seasonally adjusted annual rate up nearly a million units from August to more than 13 million.

The Detroit 3 combined for a 17.4% gain over like-2010, with Chrysler extending its year-over-year growth streak to 18 months with a 26.9% jump in sales and General Motors improving 19.7%. Ford upped sales 16.4%, with strong light-truck deliveries (up 18.2%) more than offsetting weak car demand.

European auto makers did even better, with a combined 17.9% increase over year-ago, bolstered by Volkswagen’s 35.6% uptick.

But it was Toyota and Honda sales, down 17.5% and 8%, respectively, that best illustrated the market’s ability not only to reach a 13 million-plus SAAR but also potentially sustain it.

Related document: U.S. Light Vehicle Sales – September 2011

Toyota daily sales were down 2.5% from the prior month, a better result than the auto maker’s average decline of 10% from August to September over the past eight years (putting aside the 2009 post-Clunkers drop of 42%).

September simply is not a strong month for Toyota, which focuses much of its model-year selloff activity in August, and its relatively strong performance in the month pointed to a hastening recovery for the company.

Likewise, Honda’s 13% month-to-month increase in DSR was the auto maker’s biggest August-to-September gain in at least three decades. And the 8% decline vs. year-ago, a vast improvement over four months of double-digit declines, was good enough to push Honda ahead of Hyundai/Kia for the first time since April.

Not that the Korean auto makers did poorly: Hyundai sales were up 11.8% and Kia’s jumped 18.4% over year-ago. But the low SAARs of the spring and summer – dipping as low as 11.5 million units in June after averaging more than 13 million in the first quarter – have tracked closely with inventory shortages at Honda and Toyota, whose supply chains were hit hard by the Japan earthquake and tsunami.

As those auto makers’ production has come back online and stocks have crept up in recent months (Honda’s decimated inventory grew 19% in September; Toyota’s climbed 12.5%) the industry SAAR has climbed back up with them.

It would appear that many Honda and Toyota customers have been avoiding the marketplace while the auto makers restocked. With both companies moving toward overtime production, there’s reason to believe fourth-quarter SAARs could match or exceed first-quarter rates.

Calendar-year U.S. LV sales through September totaled 9,485,612 up 10.3% from like- 2010. Model-year sales for 2011 (October 2010 through September) finished at 12,441,958 units, an 11.0% increase over the 2010 model year. Total light-vehicle inventory grew 3.3% from August to September, but is tracking 6.3% below year-ago.

jsousanis@wardsauto.com