Arsonists torched a black BMW behind factories in Dandenong.
Police appealed for information about the fire, which occurred about 9am on Friday 11 August, in Mills Road.
They believe someone poured accellerant onto the roof of the parked 1994 sedan and set it alight, causing extensive damage.
The CFA attended and extinguished the fire.
Call Crime Stoppers on 1800 333 000 with any information.