U.S. light-vehicle sales improved on year-ago for the 37th straight month in September, based on daily selling rates, while the third quarter posted a long-time high.

With two fewer selling days from same-month-2012, and the Labor Day weekend being included in August’s results for the first time since 2008, September’s raw volume of 1.133 million marked a decline from year-ago. But the DSR over the month’s 23 selling days (vs. 25 last year) increased 4.1% from September 2012.

September’s seasonally adjusted annual rate of 15.2 million units was a 5-month low. However, the third-quarter SAAR of 15.6 million was the highest for any quarter since 15.9 million in October-December 2007. The final quarter of 2013 is expected to improve on that pace, and full-year sales are forecast at 15.6 million.

Inventory levels appeared to play a big part in September’s results for several automakers.

Ford led the high-volume automakers with a 15.2% year-over-year increase in September after coming into the month with inventory up 30.6% from year-ago. Indeed, the additional inventory allowed Ford to come within 6,000 units of General Motors for leadership in the month.

GM’s inventory finished the month 8.5% below like-2012. In particular, GM was short on Chevrolet Cruze small cars and lower-priced trim levels of its new ’14-model pickups. Consequently, its sales declined 3.2% from like-2012. It also said fleet deliveries trailed year-ago, although the automaker expected them to rebound above year-ago levels in the fourth quarter.

With inventory slightly above like-2012, Chrysler finished with a hefty 9.3% gain September.

Three straight double-digit sales increases over the summer took a toll on Toyota’s dealer stock, as its Aug. 31 inventory declined by a steep 9.0% from the prior month and fell below the year-ago total for the first time since March 2012.

Still, the automaker managed a 4.0% increase in deliveries from September 2012. Sales dropped 13.5% from the prior month, however, and were well below its year-to-date increase of 8.1% through September.

Nissan, with inventory 1.8% below year-ago, recorded a lukewarm 2.7% rise in demand, as its market share declined to 7.8% in September from 8.0% both in the year-ago month and year-to-date 2013.

Honda bucked the trend. Its August inventory was 15.2% above like-2012, and increased slightly from July, but sales declined 2.1% from year-ago in September. The downturn broke a string of 22 straight increases.

However, Honda’s results likely were an anomaly. While most ’14 models industrywide begin sales in October, Honda already started deliveries of new-model-year vehicles for several key nameplates in July and August, including the Honda Accord, CR-V and Odyssey, and it might have been caught in the wake of other companies still goosing incentives on ’13 models in order to clear them from inventory.

By vehicle segment, Lower Small, Upper Middle and Luxury were the car segments recording strong gains over year-ago. Trucks were pumped by Small and Middle Cross/Utility Vehicles, Middle Sport/Utility Vehicles and Large Pickups and Vans. Also, Luxury CUVs and SUVs finished with year-ago DSRs above the industry total.

In fact, all LV luxury segments combined for an 11.5% increase over year-ago, and accounted for 13.9% of the market, vs. 13.0% in like-2012.

Most automakers heralding increases above the industry average were premium manufacturers including BMW, up 17.7%, Daimler (14.9%), Jaguar-Land Rover (10.1%) and Porsche (22.9%). Also, the Audi brand increased sales by 15.4% and Cadillac was up 19.5%.

Of the major segments, Upper Middle cars and Large Pickups had the strongest gains at 10.6% and 9.6%, respectively.

Market share for Large Pickups surged to12.4% in September, well above year-ago’s 11.8%. Year-to-date share for the segment reached 11.8%, vs. year-ago’s 10.7%.

hstoddard@wardsauto.coms