Audi leads the high-demand vehicle list

Feel like driving Audi's posh new crossover, the $38,000 Q5? The signature Audi LED taillights and leather-cloaked interior, paired with a fast engine and car-like handling, do much to separate it from the pack of premium small SUVs.

But you'll have to be quick to get one. They've been selling just four days after they hit dealer lots, says Audi spokesman Christian Bokich--and that's not likely to change anytime soon.

Audi's other hot seller, the $52,400 S5 coupe, is also difficult to get, since it sells four times as fast as the average Audi vehicle. It sold 544 units in the U.S. last month, up 38% from July of last year. Overall year-to-date sales at Audi are slightly up over 2008 as well (down just 14.6% overall, versus negative 16% at this time last year), making it one of the strongest carmakers in the American market right now.

But Audi isn't the only manufacturer with several vehicles in high demand. Detroit has a fine showing with Chevrolet's super-hot Camaro, which is sold out virtually everywhere--its sales even topped those of the iconic Ford Mustang in July. Ford's Escape and Escape Hybrid also made our list of the cars that are most difficult to get this summer.

To compile our list, we used inventory data from Wards Auto, an automotive data and analysis firm based near Detroit. We calculated day-supply rates of 2009 and 2010 model-year vehicles for June and July to get an average figure for just how obtainable these cars are this summer. (Day-supply rates are inventory numbers divided by the daily selling rate that month.) Then we spoke with manufacturers to find out how long those cars are actually sitting on dealer lots.

How long a car sits on the lot provides more insight on why some day-supply rates are lower than others: Just because a car has a short day-supply doesn't necessarily mean it hasn't also sat on the lot for months. By the same token, premium and luxury automakers are careful about over-exposing some models to the public. Even if a vehicle like the Audi S5 is in high demand--which it always is--Audi won't drastically increase the number of units it makes. The idea is to balance accessibility with rarity; once an S5 becomes ubiquitous, it loses its luster.

"Production we keep very steady because the yo-yo stuff tends to put the production cycle off quite a bit," Bokich says. "We have worked very hard in the last few years to work on inventory management with our factory in Germany and other various factories."

Toyota, in particular, has several vehicles that have been popular over the summer, and for good reason. The automaker routinely ranks high in J.D. Power and Associates quality and dependability studies, and three of the 10 top-selling vehicles last month were made by Toyota: the Camry, the Corolla/Matrix (the wagon variant of the Corolla) and the Prius.

The $22,000 Prius is an obvious option for conscientious drivers, with its high fuel-efficiency (51 mpg in the city/48 mpg on the highway) and generous amount of storage space. Auto analysts say it has single-handedly refashioned Toyota's image from that of a company that builds unremarkable sedans to the go-to manufacturer for green living.

The $16,290 Matrix and $21,500 RAV4 also speak to a recurrent theme this year in sales: the popularity of compact crossover-type vehicles, especially of the premium variety. Jeff Schuster, the executive director for global forecasting and product analysis at J.D. Power and Associates, says the segment is the only one recognized by J.D. Power that reports a year-over-year increase in sales.

While these cars sold well this summer, the effect of the Cash for Clunkers program shouldn't be overlooked--it skewed inventory levels for both luxury and non-luxury manufacturers nationwide. Current inventory levels and day-supply rates contrast sharply with this past spring's sluggish auto sales.

As of Aug. 31, according to the U.S. Department of Transportation, Cash for Clunkers had removed more than 700,000 cars from the road, with rebate claims worth $2.9 billion total. That means automakers have had to respond accordingly. GM has announced it will boost production in the fourth quarter of the year; Ford is adding 10,000 units in the third quarter, mostly for the Ford Escape, ranked No. 9 on our list, and for the Focus. And Toyota says it will increase production of its most popular vehicles by 65,000 units in 2009.