Mouse prevention
Best ive found is to have the car sealed up tight where they cant get in.
Tried all the rest of the theories and nothing has worked.We did find that leaving a pail 1/2 to 3/4s full of water in the building,they would jump in and couldnt get back out.If its really cold climate may add some antifreeze if there are no other animals(pets)present to keep from freezing.
If the car seals up good the cowl grill is usually where they come in,block it off and you should be ok,only way i have had success.