Oil is a cargo, which means it needs to be transported somehow. Most often, tankers do this, transporting raw materials by sea, but on land the tanker cannot be used and then it is replaced by a truck with a special tank body for oil, as in Oil Tank Truck Driving Sim. Go through the levels and to do this you must drive up to the parking lot and pick up the tank, then leave the fenced area and move along the road, following the arrow signs. Be careful and don't make mistakes, your driving time is limited, you have to deliver the cargo on time in Oil Tank Truck Driving Sim.
