Fill up your gas tank more often (keep your tank above half-full).

Let someone know where you're going and when you expect to get there.

Inventory your change jar, exchange it for $1 bills, and conceal that in your car.

More low or no-cost prep items for the car: water bottles, matches

Most of the preps I have in my car are old camping and hiking gear. Camping has come in very handy for prepping.