The Magnum Opus is a customisable vehicle created by Chumbucket with the help of Max Rockatansky. Chumbucket led Max to the vehicle after Max's V8 Interceptor was stolen by Scabrous Scrotus. Chumbucket showed Max the plans for upgrading the Magnum Opus, as well as how he plans to replace the V6 engine with a V8 to give it more power.
With Chumbucket's help, Max upgrades the Magnum Opus to meet the challenges ahead and surpass his lost V8 Interceptor.
Along the way, Max helps out certain Wastelanders who help him progress in boosting the capabilities of the Magnum Opus in exchange for removing the threats and presence of other factions in the areas.
Eventually with the help of Chumbucket, Max finds a V8 engine to fit the Magnum Opus so that it would be equal in terms with the Interceptor. After the Magnum Opus has been upgraded significantly, Max tracks down Scrotus and takes out his war party. This battle leaves Scrotus' Land Mover dangling over the edge of a cliff awaiting one more push to send him and his vehicle off the cliff.
Max tells Chumbucket to get off the car, leading Chumbucket to realise Max plans to use the Magnum Opus to push the Land Mover over the edge. He clings onto the hood of the car, pleading with Max not to do so as to not ruin his dream and work, but Max disregards Chumbucket's pleas and speeds furiously toward the Land Mover. He dives out at the last moment before it collides with Scrotus' vehicle.
The Magnum Opus fails to push the Land Mover over the edge and Chumbucket is killed in the collision, but gasoline leaking from the Land Mover catches fire and causes a large explosion that sends both the Land Mover and the Magnum Opus over the edge, bringing an end to the only car that had ever surpassed the Interceptor.
The Magnum Opus is unique in the sense of being the only car that Chumbucket rides with Max and having unique weapons, such as the Harpoon, Thunderpoon and Sniper Rifle.
The car has six potential bodies, some of which, like other vehicles in the game, are based on vehicles from Mad Max: Fury Road:
- Death Rattle - Based on a 1934 Chevrolet Master 5 Window Coupe
- Die Rolla - Based on 1960s Rolls-Royce
- Wild Hunt - Based on a Ford Falcon XB, similar to Max's own Interceptor
- Shovelface - Based on a 1968 Ford Mustang Fastback
- Furnace - Based on a Perentti Coupe, an Australian kit-car based on the chassis of a Chevrolet C3 Corvette
- Ripper (DLC) - Based on a 1960s Pontiac GTO