Detective Inspector Dave Lynch said police were confident Shalvin Prasad drove his RAV 4 to Plunkett Ave, Papatoetoe and then got into a car with someone unknown.
The RAV 4 was found later after a public appeal had been launched.
Mr Lynch said the killing was particularly nasty and the profiling unit was looking into any significance the petrol had.
His burning body was found in shrubs about 5m back from McRobbie Rd, Kingseat, on January 31. His family reported him missing that night and his body was identified using DNA days later.
Police and his family have said there doesn't appear to be anything in Shalvin's life that could have made him a target, but this week revealed he withdrew tens of thousands of dollars from a Manukau branch of the ASB on Wednesday last week.
There is no explanation of why he withdraw the money without his family's knowledge but detectives believe it may be linked with his death.
An accelerant was used to start the fire that killed Mr Prasad and there was no indication he suffered any injuries before being set alight. It was impossible to say whether he was conscious at the time of death, but he was alive.
Police have explained the large sum of money by saying he was a diligent saver over a long period of time but a theory is Mr Prasad - who is said to be "innocent and naive'' - may have been the victim of blackmail, bribery or fraud.
There was no indication at all Shalvin was involved in any illegal activity, Mr Lynch said.
Yesterday police announced a member of the public had handed in Mr Prasad's cellphone. The phone had been submitted to the electronic crime laboratory for forensic testing.
* Anyone with any information related to the investigation can contact police on 09 295 0311 or to Crime stoppers on 0800 555 111.
