Used vehicles sold at auctions logged their highest depreciation this year in September, as 2009-2013 car and truck models fell 1.7 percent in value, according to Black Book.

Entry mid-size cars recorded the highest depreciation for the month by falling 3.2 percent to an average of $11,601 per sale. The category that includes the Chrysler 200, Ford Fusion, Chevrolet Malibu, Volkswagen Jetta, Toyota Prius, and Chevrolet Volt has fallen 13.7 percent year-over-year.

Among the truck categories, full-size CUVs and cargo minivans showed the highest depreciation for the month with 2.4 percent (to $23,501) and 2.2 percent (to $10,946) respectively. Full-size CUVs would include the Chevrolet Traverse, Buick Enclave, Dodge Durango, and Dodge Grand Caravan.

For the third straight month, full-size passenger vans held the strongest retention and recorded the only price increase among vehicle categories. These vans, including the Dodge Sprinter, Ford E-Series, and Chevrolet G-Series, increased 0.6 percent in value to $19,143. Full-size cargo vans depreciated 0.7 percent to $20,141 for the second-best average sale price.

Other strong categories included compact pickups, which fell 0.9 percent in value to $15,692; premium sporty cars, which fell 1.4 percent to $48,830; and full-size pickups, which fell 1 percent to $26,701.