In Deadzone, Petrol is used to drive an intact driveable car.
Petrol is easily identified as a large red retangular like box with a triangle shaped top. A full can of Gasoline can hold up to 5000 gas and can be refiled by combining 2 gas cans of used Petrol.
Take a can of Petrol in your inventory and find a usable car. Enter the car and use WASD to navigate the car.
(You can enter an intact car when a PRESS Q label appears when next to one) (Petrol will be used up fairly quickly while driving so keep an eye on the amount of gas you have left while driving)