rats don't like open spaces, so i keep my rig stored away from foliage & cover w/hood open 100' or so away from cover in an open field that seems to reduce rodent damage, hood open & mothballs deter as well. the dryer sheets are less effective for me, in fact i've seen the sheets in rodent nests close by. regardsI got 2 feral cats 4 yrs ago. They live in the barn where I park my tractors and car.
Kitty has been sleeping on the hood. You just know there aint no mice around. Prior to barn cats we had all sorts of rodent problems like engine nests and chewed wiring.
Now my only problem is feeding and watering them ~ easy peasy and effective solution.