The mechanic who claimed New Zealand woman Karen Ristevski's husband never mentioned a faulty fuel gauge has said he made a mistake.

The mechanic of the murdered woman previously made a statement to police, saying he found nothing wrong with her Mercedes Benz after Ms Ristevski's husband Borce told police he was driving his wife's car the day she went missing to fix a faulty fuel gauge.

He took the car on a drive on June 29 last year and told police he hit a bump in the road and the fuel gauge corrected itself and he drove home.

The mechanic originally told the Herald Sun: "In all my time working on Mercedes Benz cars, I've never come across this type of problem before."

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But the mechanic, who runs the Mercedes Benz Service Station in Keilor East, in Melbourne's northwest, received a phone call from Mr Ristevski on Wednesday, reminding him he did tell him about the fuel gauge.

Ten News was interviewing the mechanic about his statement to police when the phone rang.

On the other end was Ms Ristevski's husband.

"I thought it was about three years (ago when I last serviced the Mercedes) but he said it was two years ago," the mechanic said following the phone call.

"He mentioned the fuel gauge to me (today), but I didn't do the job (originally) so I didn't remember it."

The mechanic now recalls Mr Ristevski had in fact told him about the fuel gauge during the last service and he told him to take the car to an automotive electrician.

"I didn't do the (electrical) job - that's why I don't remember it," he said.

Ten News reports the automotive electrician did not have a record of a car service.

A Mercedes expert has previously challenged claims the 2004 Mercedes-Benz SLK 200 coupe were made with faulty fuel gauges.

Experts told Fairfax Media the car was "not an FJ Holden" and would not be fixed by simply hitting a bump.

Nick Theodossi, of Nick Theodossi Prestige Cars, said he had never heard of this happening in the 35 years he had been working with Mercedes cars.

Another mechanic told Fairfax there were two sensors in a Mercedes fuel tank, meaning both would have to be broken to give a false reading.

Borce and Karen Ristevski. Photo / Facebook
Borce and Karen Ristevski. Photo / Facebook

Investigators have named Mr Ristevski as the number one suspect in his wife's murder.

There is no suggestion he committed the crime.

Ms Ristevski, 47, went missing from their luxury A$1.1 million Avondale Heights home in Melbourne's northwest after fighting with her husband about money.

Eight months after she walked out the door her decomposed body was found between two logs in bushland at Mount Macedon, an hour's drive northwest of Melbourne's CBD.

In December police conducted a two-day search for the missing mother at Gisborne and Toolern Vale in Melbourne's northwest.

She was found in February about 25km from this search area.

The search began after phone towers tracked mobile phones belonging to Ms Ristevski and her husband in the area.

Mr Ristevski told police he was driving Ms Ristevski's car in the area when the fuel gauge corrected itself. He claimed he did a U-turn and went home.

In July, police retraced the steps of the black Mercedes as part of the investigation.

In June police released new CCTV images that show a car they believe is Ms Ristevski's Mercedes.

The vehicle, which has Mercedes-manufactured five-spoke wheels, is pictured driving northwest along Old Calder Highway over a railway crossing in the northwest Melbourne suburb of Diggers Rest at 11.12am on the day she disappeared.

Police suspect the car may have been driven further northwest to Gisborne or Mt Macedon about noon the same day.

One theory police are working on is that Mr Ristevski was driving the car in Diggers Rest at the time the CCTV was captured and that Ms Ristevski's body was in the vehicle, according to the Herald Sun. The Mercedes was the last of six vehicles seen driving close together in the suburb.

There have been a number of bizarre explanations for Ms Ristevski's murder.

Mr Ristevski's son from a previous marriage, Anthony Rickard, claimed Ms Ristevski was going to leave her husband as they had been having an affair.

Following her disappearance, Mr Ristevski's brother, Vasko Ristevski, claimed she had fled the country on a fake passport.

Police said Missing Persons Squad detectives continued to investigate the death of Ms Ristevski and the investigation remained ongoing.