The auto industry sales had a strong September. Last month’s U.S. vehicle sales were at their highest levels since February 2008. The good news is partly due to pent-up demand and cheap easy credit.  

Vehicle sales reached a seasonally adjusted annual rate of nearly 14.9 million in September — nearly 14% higher than for the same month last year. Pent-up demand is responsible for much of that growth, with the average age of vehicles on the road at a historical high of nearly 11 years. Affordable and attainable auto loans also played a role in rising sales, with rates hovering in the 3.5% range and an easing of financing for buyers with lower credit scores.

Here’s a quick breakdown for the top five manufacturers:

GM: The U.S. sales leader is still No. 1, but its year-over-year growth was flat. GM delivered a total of 210,245 vehicles in the month, up a disappointing 1.5% (versus expectations of 2.5%) over last September, according to industry tracker Autodata. Passenger car sales soared 29.2%, led once again by the Chevy Cruze, which is now the top-selling small car in the U.S. However, the ever-popular Chevy Silverado pickup lost speed, and GM’s light-truck sales across all brands fell by more than 12%.

Ford: Ford’s sales actually slipped by 0.2% to 174,454 in September — only 2,544 more vehicles than third-place Comeback Kid Toyota. Passenger-car sales rose a slim 1.6% –  headlined by more than 90% growth in Ford Focus deliveries. Although the F-Series pickup delivered its best sales in five years, light-truck sales fell by 1% over the same month last year.

Toyota: TM was September’s star, delivering a total of 171,910 vehicles during the month — a 41.5% gain over the same month last year. Passenger cars, led by the fuel-efficient Corolla, Camry and Prius, grew by 45.6%, while sales of light trucks like the Tacoma midsize and RAV4 compact SUV grew 36.6%.

Chrysler: The Fiat subsidiary isn’t just selling more cars in the U.S. but more Fiats: The brand rose by more than 50% in September. All told, Chrysler sold 142,041 vehicles last month, an increase of 11.5% over September 2011 and the 30th straight month of year-over-year growth. Passenger-car sales rose 26.,6%, while light-truck sales rose a more subdued 6.2%.

Honda (NYSE:HMC[2]):  HMC delivered 117,211 vehicles last month, a 30.9% boost over the same month last year. Passenger-car sales surged more than 43%, fueled by the midsize Accord and the small CR-V sport utility.

So, what trends emerged from August’s vehicle sales data? Here are four:

1. Consumers Are More Optimistic. Despite 8.1% unemployment and the federal government’s looming “fiscal cliff,” consumers are feeling more optimistic about the economy, fueling big purchases like cars and homes. The Conference Board’s Consumer Confidence Index[6] rose to 70.3 in September — a 9% gain from August.

2. Toyota Is Back. It’s been a tough couple of years for the Japanese giant: The massive 4.2 million-vehicle recall from late 2009 through early 2010 bruised the brand’s reputation. And the March 2011 earthquake, tsunami and nuclear disaster in Japan created massive shortages of popular models. But now Toyota is moving forward to recapture the coveted top spot in the U.S. market — and that could happen sooner than we thought just three months ago.

3. Recall Headaches Are Spreading. TM’s sales gains come as other automakers are dealing with their own recall challenges. Nissan of North America this week issued a recall[7] of nearly 2.5 million vehicles — including 2012 Pathfinders, Xterras and Frontiers over faulty wheel hubs. Honda has expanded its May recalls[8] of V-6 Accords for potential fire risks to cover an additional 572,000 vehicles. GM this week recalled[9] nearly 41,000 vehicles, including the Chevy Cobalt and Pontiac G5, over a potential fuel leak. In its third embarrassment in less than two months, Ford recalled 7,600[10] of its newly redesigned Escapes over potential coolant leaks.

Is the rush to meet the surge in consumer demand leading carmakers to take their eye off quality?

4. Car-Sharing Could Impact Future Demand. While the automakers’ sales gains are great news for an industry that has survived the Great Recession and GM’s and Chrysler’s bankruptcies, they must plan now to weather paradigm shifts in future driving and auto-buying behavior. The so-called “peak car” trend suggests that younger consumers in the U.S. and Europe will be less likely to buy cars — or even acquire licenses — in the near future, according to an article in The Atlantic[11].

If, indeed, car ownership is headed for decline — and alternatives like carpooling or car-sharing become the “new normal” — automakers need to be more prepared than they were when high gas prices demolished demand for gas-guzzling land yachts in the 1970s. GM already is facilitating peer-to-peer car-sharing[12] by making its OnStar application programming interface (API) available to RelayRides, enabling individual owners that subscribe to the satellite service rent out their vehicles to other users.

What the long-term impact of such services will be on sales to consumers remains to be seen — and to be closely watched.

Blog post (recap) by Susan Aluise