For the 38+ years out here its been - - me vs the mice. I've tried just about everything. Traps, moth balls, "walk the plank" mouse traps, etc.
For me - barn cats work the very best. I've got three now.
My problem has always been the nest they build and the dog food they pack away in the engine compartments of my cars & trucks.
Finally I found a way that, for the last nine months, has TOTALLY kept them out of the engine compartments.
I open the hood and leave it open. I guess the open engine compartment just isn't that inviting. For whatever reason - they no longer enter the engine compartments. I've never had them in the passenger compartments.
I don't have squirrels. The open hood technique keeps the chipmunks out also.
Now I can concentrate on those miserable pocket gophers. Hopefully the barn cats might find them tasty also.