Applying a motor oil undercoat to protect your car from rust in the winter is not difficult. This type of undercoat on the car undercarriage protects the car against rust because it keeps the salt used to clear snow from streets from adhering to the vehicle. An oil undercoating is less expensive and works more efficiently than the rubberised coatings offered at dealerships. Rubberised coatings tend to chip and peel over time, trapping the salt and allowing the vehicle to rust even more quickly.
Drive the car onto a set of drive-on-ramps so you can easily access the front underside of the vehicle. If you don't have ramps, use jack stands or an automotive lift. Follow the lift precautions and packaging instructions to raise the car. Be sure that the car is on a flat, level surface to start.
Attach a pressure sprayer to your garden hose and rinse the undercarriage of the car thoroughly. Start under the engine and transmission. Follow by rinsing under the fenders and wheels. Scrub with a stiff brush to loosen dirt. Rinsing the undercarriage of the vehicle will remove dirt and any salt that may already be rusting the underside of the vehicle. Allow the undercarriage to dry for two hours.
Attach a sprayer to a compressor. Disconnect the plastic container from the sprayer and pour used motor oil in the container. Turn the compressor on and spray the undercarriage using horizontal movements. Spray under the fenders and in the tire wells to prevent salt from rusting these areas. Spray the underside of sheet metal, joints, rocker panels and inside door seams. Avoid spraying wires, the oil plug and exhaust pipe.
Lower the front of the vehicle and raise the rear of the vehicle. Spray the rear underside of the vehicle. Avoid spraying the exhaust pipe.