The 1984 Castrol 500 was an endurance motor race staged at the Sandown Park circuit in Victoria, Australia on 9 September 1984. The event was open to Group C Touring Cars, competing in two engine capacity classes, Up to 3000cc and Over 3000cc. It also included a class for Group A cars which were to replace Group C cars in Australian Touring Car racing in 1985. The race, which was held over a distance of 503 km, was Round 3 of the 1984 Australian Endurance Championship.
This was the first Sandown endurance race where the distance was 500 km and the first of five races on the new 3.878 km (1.928 mi) long 'International Circuit'. Prior to 1984 the Sandown Enduro had been held over distances including: 6 Hours (1964–65), 3 Hours (1968–69), 250 miles (1970–75) and 400 km (1976-83), all held on the old 3.100 km (1.926 mi) circuit. The meeting also saw the opening of the new International standard Sandown Park with changes including the relocating of the pits from between turns 1 and 2 to a new $600,000 pit complex at the start of the main straight, and the lengthening and re-profiling of the circuit to the minimum length required for an International circuit of 3.9 km, primarily by the inclusion of an 800-metre infield section, which for the first time saw the circuit cross to the inside of the venue's horse racing track.
Nissan driver George Fury sat on pole in his Bluebird Turbo with a time of 1:46.2 for the new track. Alongside Fury in a brand new Roadways Racing Holden VK Commodore was Allan Grice who was only 0.1 behind. Filling out the second row of the grid was newly crowned Australian Touring Car Champion Dick Johnson in his "Greens-Tuf" Ford XE Falcon, and the Holden Dealer Team VK Commodore of Peter Brock. The third row of the grid consisted of the top two finishers from 1983. Winner Allan Moffat in his Mazda RX-7 and Jim Richards in the JPS Team BMW 635 CSI.