A Melbourne grandfather was dragged from his car and threatened with assault by two carjackers who then sped off and crashed his luxury Mercedes.

Two men approached 71-year-old Maurice moments after he got in his in his white Mercedes-Benz in a Hampton East shopping centre car park about 4.20pm on February 17.

"Someone just pushed me from the passenger side to the other side and another gentleman grabbed my arm and pulled me out of the car," Maurice, who did not want he surname published, told reporters on Wednesday.

Maurice said he was threatened with assault if he did not hand over his keys, which he did.

"My life's more important than a key and a car," he said.

"If they're brazen enough to be in the car park, he'd be brazen enough to knock me over."

The grandfather of five said the crime has affected his health and he was having trouble sleeping.

"They're pretty low, I'm a law-abiding 71-year-old man, you don't expect to get assaulted by blokes in their 20s or 30s and it's made me feel very vulnerable," he said.

The car was then involved in a minor crash in Heatherton about 15 minutes after the carjacking before the pair, of Pacific Island appearance, dumped it in Clarinda.

One of the thugs, aged in his early 20s, was wearing black trackpants with white stripes and a grey jumper.

He was carrying a black bag, black hat and wearing white shoes.

The other attacker, also in his 20s, wore black pants, vest and hat and a grey t-shirt with a black.

The pair are believed to have been hanging around the carpark for at least an hour before the attack, and any witnesses are being urged to speak to police.