"Two days ago, I saw a vehicle that will haul that tanker...You want to get out of here, you talk to me..." - Max , speaking to the survivors at the refinery.
The truck is a Mack R-600 Coolpower as indicated by an aftercooler mounted to the side of the cylinder head. It uses a tip turbine fan to boost and ram air over this aftercooler. It also utilizes 2 air cleaners and sometimes had vertical bar shutters to open and shut in front of the radiator to maintain proper temperature.
The engine could have been either 285, 300, 320 or 350 horsepower, depending on fuel pump, injector and turbo combinations. The cab of this truck seems to be early 1970 till about 1978 model, based on the old style roof clearance lamps.
Appearances on screen
A Mack R-600 plays a critical role in the events of Mad Max 2 . Max first finds the truck shortly after the events of the opening chase. One of the Marauders' vehicles that had been chasing Max crashes into the truck's trailer.
Afterwards, Max finds that the Mack's fuel tanks are dry, and after making a grim discovery in the truck's cab, he moves on.
Note: Spoilers Below
Max later returns to the truck in order to recover his own vehicle. With the aid of the gyrocopter, he returns to the Mack with fuel that he received from the refinery. He manages to get the rig started, and detaches it from its trailer, which appears to contain a variety of household items.
While attempting to return to the refinery, Max drives the truck past the Marauders that surround the refinery. In his attempt to get through, the truck is temporarily disabled by a well-placed shot fired by Humungus at the truck's radiator. Max manages to limp the vehicle back through the gates of the compound.
The parapalegic mechanic and his assistants manage to repair the tanker's engine. The truck is attached to the fuel tanker trailer, and is also fitted with a protective metal plate to protect the radiator and cow-catcher-esque front end. The trailer is also modified so that two people can ride on it and attempt to fend off marauders.
When exiting the refinery, Humungus fires what remains of his ammunition at the front of the Mack, but the protective metal plate absorbs the shots.
The marauders continue to harass the tanker as it drives away, shooting out some of the tires in an attempt to slow it down.
The tanker is not stopped until Humungus rams his nitrous-fueled truck head on into the tanker at high speed. Humungus' truck disintegrates on impact, and although the tanker-truck remains in one piece, it is severely damaged and rolls over off of the road.
When it is realized that the tanker was merely a decoy filled with sand, what remains of the marauders withdraw.
The writing on the side of the trailer and truck says "The vermin have inherited the Earth".
It is a quote from the original script for The Road Warrior that was used in tandem with a shot from Mad Max for the opening montage. The scene was scrapped but the line "The vermin had inherited the earth" had made it into the movie as the writing on the side of the trailer and the tuck.
Ir. A GROUP OF OUTLAW BIKERS... ... leap from a hillside onto the roof of a moving fuel tanker. They pass a hose into the tank.. NARRATOR V/O At last, the vermin had inherited the earth.