CarGurus looked at 900 million used car searches and the results probably aren't surprising, but are good to know. Full story here.
The big three had 5 of 6 top spots for nameplates. Chevy finished first overall with Ford in second place, with Toyota in third. 

Mustang and F-150 were 1 and 2 on the model search list, with Silverado, Corvette, and Camaro filling spots 4-6. Jeep Wrangler grabbed the third spot. 

Does this match what you're seeing in your stores?