Tariq Khan says he can feel it in his gut.
When he sees a used car or truck he knows he can sell for a healthy profit, the auto dealer from Villa Park, Illinois, jumps on it.
"I walk around it, check the record, but it's ultimately a gut feeling," Khan said. "You have to buy the right car at the right price."
For Khan, the right price for a 2004 Lexus LS 430 was $7,500.
"I'll probably sell it for nine or 10 grand," he said.
Khan is one of several hundred auto dealers who spent a rainy day at the Manheim auto auction in Matteson, Illinois, where thousands of used cars are bought and sold.
"Very few people realize used car sales are probably three times bigger than the new car industry sales. The used car industry really fuels what happens with auto sales," said Sandy Schwartz, president of Cox Automotive, which, like Manheim, is a subsidiary of Cox Enterprises.
Dealers don't need to be told. They're riding a bull market that has steadily driven the number of used cars sold to an expected total of 41.5 million this year, an increase of 1.5 percent from 2013, according to IBISWorld.