"It's the perfect time," said Joe Santoro, owner of BJ's Complete Auto Repair at 3820 N. Harlem Ave. "They're going to be looking."

Santoro said rodent infestation in vehicles has been "pretty rampant" and "explosive in the last three to five years." He estimated that of the roughly 2,500 cars his shop sees annually, 40 to 50 this year had some degree of rodent infestation — a small percentage, but one that is increasing.

At the time he spoke, a Ford pickup was in his garage awaiting parts to replace wiring and foam chewed through by what was likely one or more rats.

Part of the problem, Santoro said, is the city's rodent population, along with auto components now made with soy-based materials that appear to attract hungry rats.

Pete Rosquete of Doc Able's Auto Clinic in Evanston recalled one customer who left a second car parked on the street. "They got in under the carpeting in the back . . . they made a mess . . . we had to take the back seat out," he said.

Leo Hernandez of Eliot's Complete Auto Repair at 3658 N. Lincoln Ave. described a customer who came in earlier this year complaining of a foul smell whenever he sprayed windshield wiper fluid. "Turned out there was a dead rat in there," inside the reservoir, Hernandez said. "We pulled it out and the rat was blue."

The problem is not unique to Chicago. A 2017 study by the National Pest Management Association found that nearly a third of Americans have experienced vehicle damage from rodents. Mark Friedlander of the Insurance Information Institute said nearly 100,000 comprehensive auto claims are filed annually in the U.S. because of rodent damage to car wiring.

Repair costs vary widely. Friedlander said minor repairs typically run $500 to $1,000, while more significant fixes range from $1,000 to $6,000. "However, we have seen claims run as high as $10,000-plus for major damage," he said.

State Farm spokesman said 2025 data showed the average comprehensive claim payment for rodent-related vehicle damage was approximately $3,900 nationally. The Illinois-based insurer ranks rodents as the second most common animal involved in claims. Such damage is typically covered under comprehensive coverage, not collision.

Mechanics offered various deterrents. Rosquete said his shop uses peppermint-scented repellent sold at home improvement stores. Santoro recommends moth balls in the corners of the engine area. Hernandez suggests repellent bags available online.

Richard Cao of the Automatic Trap Co. said that while he sells traps, he generally advises against using them inside a vehicle. "We try to avoid anything dying in your compartment," he said, adding that changing the environment is more important — keeping trash bins sealed and areas clean.

Experts also warn against using toxic poisons, which can sicken or kill animals higher up the food chain, such as cats and birds of prey, that feed on poisoned rodents.

Hernandez advised motorists to drive their cars regularly, especially if parked near an alley, and to avoid parking near trash bins or in garages with bird seed or pet food.

Chicago's Department of Streets and Sanitation handles rodent problems in public settings, fielding between 40,000 and 45,000 rodent calls a year, but does not address private vehicles.

Michael Bentley of the National Pest Management Association recommended regularly checking engine compartments and seeking a licensed exterminator if an infestation is found. He noted that modern vehicles contain more electronics than ever, giving rodents more to chew on — something they do even when not hungry.

Other animals, including cats, sometimes take refuge in engine areas for warmth rather than to hunt rodents, mechanics said.