Green’s Dictionary of Slang

1. a heavy drinker.

1975

J. Braithwaite Regulation, Crime, Freedom 231: Reactance may be strong with the young, male drunk driver - who is a ‘petrol head,’ proud of his capacity to hold his drink.

2. (Aus.) a devotee of motor-racing; also attrib.

1987		Max Harris in Australian 28 Nov. Mag. 2: A drug-sponsored Formula One Grand Prix provides an orgiastic social outbreak of hoons, goons, and petrol-heads [GAW4].
1990		T. Winton Human Torpedo 93: This was definitely [...] a bogan car. Bogs. Rockers. Petrolheads.
2000		Indep. Rev. 25 Feb. 7: A car magazine aimed at true petrol-heads.
2004		Brisbane Instit. 18 Nov. 🌐 The ‘Indy Carnival’, a ‘celebration’ for petrol-heads and suicide blondes.
2011		BBC World News (SA) [TV ad for motor-racing coverage] From 17th - 20th March petrolheads will be celebrating.
2017		V. McDermid Insidious Intent (2018) 92: With his petrol-head world view Kevin knew the dual carriageway [...] would be the perfect drag strip.