This summer's auto sales have been so sizzling that dealerships are running short of the hottest new models. Last month, 27 models spent an average of fewer than 30 days on dealers' lots before being delivered to an eager buyer, about half the average that automakers consider optimal. The in-demand models span the spectrum from luxury SUVs to performance cars, Kelley Blue Book reports.

Most wanted: Land Rover's pricey LR4 and Range Rover SUVs. With gas prices moderating, boxy vehicles are back in vogue. There is only an 11-day supply on lots of the new Lincoln MKC compact crossover ""a very new vehicle ... in a really hot segment," says Ford sales analyst Erich Merkle. Chrysler, meanwhile, is short of Ram pickups, Jeep Grand Cherokees and Wranglers. General Motors says its premier performance car, the Chevrolet Corvette, and its biggest SUVs, including the new Cadillac Escalade, GMC Yukon and Chevrolet Tahoe, won't stay on lots. ""Every one we get, we're selling,"" says Inder Dosanjh, a GM dealer in Dublin, Calif. ""No rebates, no special leases, not even $100 off the car."" Some barely touch pavement. Dosanjh says he has pre-sold all the Escalades that he has been able to snag. Some dealers say they tried to prepare for the crunch. ""We've been selling like crazy, and we beefed up,"" says Adam Lee, chairman of Lee Auto Malls in Maine, where sales at his two Chrysler dealerships have been strongest since the 2003. Typically, August is the best time of year for a car deal, according to a car-buying website TrueCar, with average selling prices $169 below the next-lowest months. But for models in short supply, there likely will few deals for buyers this month. Automakers are hesitant to step up production after having been burned before on oversupply when the recession hit. Chrysler Group CEO Sergio Marchionne told investors last week that he is squeezing all he can out of existing plants, but he doesn't plan to add factory capacity. That discipline can cost some current sales. ""If we could get our hands on more inventory, we could sell more,"" says Fred Diaz, senior vice president for Nissan's sales in the U.S. His most in-demand vehicle: ""Rogue (compact SUV) is on fire,"" he says. With six hot models, Subaru's Dominick Infante says ""Virtually all of our cars are short supply. Cars are selling as they arrive on the lots."" Vehicle models that averaged less than 30 days at dealerships in July:

Vehicle/days on lots

Land Rover LR4 7.8. Land Rover Range Rover 11.5 Lincoln MKC 11.7 BMW M4 12.0 Mercedes-Benz CLA-Class 12.2 Chevrolet Impala Limited 12.7 Subaru Forester 14.1 Land Rover Range Rover Sport 14.3 BMW M3 15.5 Ford Focus ST 16.5 Toyota Highlander 16.7 Subaru WRX 17.4 Toyota Tacoma Double Cab 17.8 Audi RS 7 18.0 BMW X5 18.0 Toyota Tacoma Access Cab 18.6 Subaru XV Crosstrek 20.8 BMW i3 21.6 Chevrolet Corvette 22.1 Lexus GX 22.2 Toyota Tacoma Regular Cab 22.9 Nissan Rogue 26.6 Subaru Legacy 27.0 Toyota RAV4 27.8 Lexus RX 27.9 Mercedes-Benz GL-Class 28.3 Subaru Impreza 28.3.