If it’s impossible to keep them out, what’s the best way to kill them? At least one is living in my car, chewed through seatbelt, stole my keys.
I’ve had good luck with both mice and rodents with electronic sound device. I’ve heard not all work, and not on every pest, but I lucked into one that did. I feel it’s worth the experiment. Otherwise it’s trap and kill that works best for me preferably outside the car but in if necessary and inside a garage. Then continue keeping all fresh air vents closed including recirculating control.