The 1985 Castrol 500 was an endurance race for "Group A" Touring Cars staged at the Sandown International Motor Racing Circuit in Victoria on 15 September 1985. Race distance was 129 laps of the 3.878 km (1.928 mi) circuit, totaling 500.262 km. The field was divided into three classes according to engine displacement. * Class A : 3001cc to 6000cc * Class B : 2001cc to 3000cc * Class C : Up to 2000cc The event was Round 3 of both the 1985 Australian Endurance Championship and the 1985 Australian Manufacturers' Championship. There were 36 starters, of whom 18 were classified as finishers.