Police were told the man and his wife left a dinner party in Essendon, in the city's northwest, between 1.30am and 2am (AEDT) on Saturday and drove to their nearby home in Grice Crescent.
It's alleged that as the man was getting out of the car, four men attacked him, pushed him back against the vehicle and poured an unknown fluid on him.
One of the men then ignited the fluid with a lighter before all four men fled.
The victim then allegedly ran from the car while peeling off his clothes.
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The man suffered burns to 15 per cent of his body including his arms, chest and face.
A police spokeswoman said investigators did not yet know of any motive or circumstances surrounding the attack.
The incident is being investigated by the arson and explosives squad.
