Buying a car privately without change of ownership in Greece

I have heard I can buy the right to use someone's car in Greece, as long as I pay for the insurance and upkeep. It's the insurance papers that are necessary for being on the road, not the ownership papers, albeit with a written authority from the owner of course. Is this correct ? I own a house in Corfu, but do not stay more than 3 months a year in total, and therefore do not have a resident visa. I am English.

@damienduk I thought as long as the car was insured, anyone with a driving licence is insured to drive the car. Would you need additional paperwork?