I've posted links here before about using this non poisonous homemade rat and mouse killer. Here's a link to a 3 year follow up with one of the original posters of the mouse killer videos:
https://www.youtube.com/watch?v=ZLvpNIO84hA
I first stumbled across it on You tube a couple years ago and tried it. I live in a 120 YO farmhouse and we have a stone foundation that has all types of voids and ways for rodents to get into the house. At that time I had a mouse problem and figured it wouldn't hurt to try it. I used some Planters peanut jars with a couple 1 inch holes drilled about an inch and a half from the bottom opposite each other.
The first night I placed it in the kitchen there was baking soda and muffin mix all around the jars. The second day much less powder around the jars, and the activity was less and less each day. Within a week there was no more bait being scattered, nor any evidence of traffic in the jars. The evidence of droppings stopped completely. It flat out works because rodents love wheat based bait. The baking soda causes gas internally when it mixes with their stomach acid, their digestive tract can't release the gas fast enough, their digestive tract ruptures, and they bleed internally.
If you made up a few jars and left them in and around the car in the fall, it should kill them all through the winter. I hope this helps someone save their car from the mess that rodents make, and the expense and work of cleaning it up in the spring. Bonus is no poison in the carcass in case a dog or cat eats the leftovers, safe around kids too..............
