With supplies of petroleum nearly exhausted in the near future following a major energy crisis and a global nuclear war, ex-Main Force Patrol officer "Mad" Max Rockatansky (Mel Gibson) roams the now-depopulated and desolate desert in his scarred, black supercharged V-8 Pursuit Special several years after the events of the first film, scavenging for food, water, and fuel. His only companions are an Australian Cattle Dog and a rare functioning firearm   a sawn-off shotgun   for which ammunition is very scarce.
While trying to escape a group of gang members   led by a crazed motorcycle rider named Wez (Vernon Wells) - Max manages to crash two of the gang member's vehicles and injure Wez; recognising his defeat, Wez flees. After collecting some fuel from the destroyed cars and checking a nearby Mack semi, Max inspects a nearby autogyro for fuel. Its pilot, the Gyro Captain (Bruce Spence), ambushes Max and manages to capture him briefly before being overpowered. In exchange for his own life, the pilot guides Max to a small oil refinery nearby. Max arrives to see the facility is under siege by a gang of marauders riding a motley collection of cars and motorbikes. The gang leader, known as "Lord Humungus" (Kjell Nilsson), tries to convince the refinery's defenders to surrender the facility in exchange for safe passage out of the area.
A group of defenders attempts to break out of the compound, but the marauders capture, torture, and kill all but one of them, who is rescued by Max. Max makes a deal with the mortally-wounded sole survivor: he will bring him back to the compound in exchange for a tank of fuel. The man dies shortly after they enter the facility, and the facility leader, Pappagallo (Michael Preston), reneges on the deal, saying it died when the survivor died. His group is on the verge of killing Max when the marauders return, and Humungus repeats his offer. When the Feral Kid (Emil Minty) kills Wez's male companion, Wez becomes enraged, urging his leader to take the compound; Humungus wrestles Wez into submission, but placates Wez by revealing he has no intention of letting any of the settlers leave. Max offers Pappagallo a different deal: he will retrieve the abandoned Mack semi-truck, which is capable of hauling the tanker trailer that the facility inhabitants use to store the fuel they refine, in exchange for freedom, his vehicle, and as much fuel as he can take with him. The group accepts, but keeps Max's car to ensure his co-operation. Max sneaks out, locating the Gyro Captain (dragging the branch he is chained to) and conscripts him to help find the truck using his gyrocopter.
After finding the truck, Max drives it back to the compound, evading Humungus's men. The defenders want Max to escape with the group, but Max opts to collect his petrol and leave. However, his attempt to break through the siege fails: Wez gives chase in Humungus's nitrous oxide-equipped car and runs Max off the road, wrecking his vehicle and severely injuring him. The marauders kill Max's dog with a crossbow, then attempt to siphon the fuel from the Pursuit Special's tanks, but trigger an explosive booby trap, which kills some of the attackers. Left for dead, Max is rescued by the Gyro Captain as he is trying to crawl back to the refinery.
With no other means of escape and with the refinery's defenders preparing to depart, Max insists on driving the repaired truck. He leaves the compound in the heavily-armoured truck, accompanied by the Feral Kid he has befriended and by other inhabitants aboard as defenders. Pappagallo escorts him out in a captured marauder vehicle. Humungus and most of his warriors pursue the tanker, leaving the remaining inhabitants free to flee the compound in a ramshackle caravan and buses, blowing up the refinery as they leave. Pappagallo and the other defenders of the tanker, as well as numerous marauders, are killed during the chase and the Gyro Captain is shot down. Max and the Feral Kid find themselves alone, pursued by the marauders. Wez manages to board the truck and attack Max, but a head-on collision with Humungus's car kills both Wez and Humungus. Max loses control of the tanker and it rolls off the road. As the injured Max carries the Feral Kid from the wrecked tanker, he sees not petrol, but sand, leaking from the tank.
The truck and its trailer are thus exposed as a decoy, allowing the other settlers to escape with the precious fuel in oil drums inside their vehicles. With Pappagallo dead, the Gyro Captain succeeds him as their chief and leads the settlers to the coast, where they establish the "Great Northern Tribe". Max remains alone in the desert, once again becoming a drifter. Years later, the Feral Kid, now the Northern Tribe's new leader (voice by Harold Baigent), reminisces about the legend of the mythical "Road Warrior" (Max) who now exists only in distant memory.
Output: What was leaking from the tanker after the collision?