Another woman was injured in the mishap which took place near Potaner village where the tanker collided with the Swift car, they said.
All the victims, some of them related to each other, were travelling in the car which was going to Mumbai from Mahad town while the tanker was coming from the opposite direction, police said.
Four of the car passengers - Sunil Gadkar, Suchita Manohar Salvi, Sangeeta Manohar Salvi and an unidentified woman - died on the spot, they said.