[Steve_Mack_CT]

Experience based response:

1) mice can indeed get into a closed car even if one tried to take basic precautions like buttoning up any openings in floor or firewall area

2) They can migrate in earlier in the season than you might expect.

3) They like NEW L-B headliners (little bas*****)

Always a tough battle, but they do find a way in. many posts out here on usual remedies - good luck; I would only suggest bolstering any efforts to block access with a repellent of sorts. I am using "Shake Away" right now but a little discouraged to find mice droppings near the packet I left in one of my cars a few weeks ago. Mothballs I think still tend to work best but the smell can be a bit much.