The dealer, Aymen Halak, said he purchased the used Nissan Altima at an auction in Oklahoma City, but he quickly noticed that something was strange.
“The car was fine, up until a test drive. We found out there's a problem in the fuel tank," Halak, owner of Unique Motors LLC in Wichita, Kansas, told ABC affiliate KATE.
“I bought a new fuel pump, took the gas tank down to replace the fuel pump to find out it's full of drugs.”
The vehicle turned out to have 26 pounds of crystal meth and one pound of heroin hidden inside -- a stash police said could fetch as much as $400,000 on the street, according to Halak.
He said he immediately notified the police, who quickly swarmed his dealership for more than five hours.
Halak said he had a customer lined up to buy the car, but police officers said it had to be disassembled.
It definitely wasn't the outcome that the car dealer expected, but he says he doesn't regret turning the car in.
"I think I did the right thing," Halak said.
It's not clear how the drugs ended up in the Nissan's tank, but authorities say it isn't uncommon for drug smugglers to use vehicles to hide drugs.
The drugs, bundled in multiple small bags, were hidden in various places inside the vehicle, including a spare tire and inside the car's doors.