To undercoat your car with oil, raise the vehicle above the ground level to access its underside from the front end, clean the undercarriage, wheels and fenders with water, and spray motor oil on the undercarriage using a sprayer attached to a compressor. Spray the underside of the vehicle's rear end in a similar fashion.
Begin undercoating your car with oil by parking the vehicle on an even and flat surface. Using an automotive lift or a jack stand, raise the vehicle to access its underside from the front end. Alternatively, position the car on drive-on ramps.
To clean the vehicle's undercarriage, connect a pressure sprayer and a garden hose, and spray water on the transmission and engine areas and on the wheels and fenders. Use a stiff brush to scrub off accumulated dirt and salt. After cleaning, let the undercarriage air-dry for a couple of hours.
To spray the oil, fill the sprayer's plastic container with motor oil, attach it to the sprayer, and connect the unit to a compressor. Then, switch on the compressor, and spray the oil on the car's undercarriage. Move the sprayer in a horizontal direction to apply the oil uniformly.
Also, spray oil in the tire wells and the bottom sides of the fenders, inner door seams, rocker panels, joints and sheet metal. Do not spray oil on the exhaust pipe, electrical connections or oil plug.
Next, bring the car's front end to the ground level, and raise its rear end in a similar manner. Repeat the entire process to undercoat the vehicle's rear side.