The mystery is his Chrysler Special, built in 1929 and which he raced in the Ngapara hill climb yesterday.
While some things are obvious about the car, who designed it, built it, where it was raced and its contest results in the early days remain a mystery.
Competing at events like the hill climb organised by the Otago Sports Car Club and North Otago Vintage Car Club was a way way of finding someone who could contribute something about the car's history.
"Someone might say: 'I know someone who owned a car like that' and I'll follow up. It usually doesn't work out," Mr Frew said.
But he keeps trying.
The former Windsor man, now retired to Ashburton, bought the Special about six years ago when he saw it advertised from a Kaikoura private collection. He was the only one who phoned about it.
Little was known about the car's early history.
It was built in 1929, has a Chrysler flathead six (P25) engine and it was obvious from the design the Special was originally designed for dirt track speedway, pretty much the only car racing available before World War 2.
Over the years, it has had bits added and removed and undergone design changes.
In typical Kiwi fashion, a mixture of bits has been used to make it up, including two kitchen sinks bolted together to make the fuel tank behind the single seat. The radiator is from a David Brown tractor and the front axle from a 1934 Dodge.
That seat was fitted by Mr Frew, made from a 44-gallon drum shaped to fit him.
He also changed the wire rims from Vauxhall units to Jaguar XK spec, so they were strong enough for his sort of racing.
Like others before him, "I'm always tinkering with it", although Mr Frew said the Special was reliable and simple to maintain.
It is not street legal, but Mr Frew takes it to classic race meetings.
Mr Frew was one of 34 entrants in the hill climb yesterday who came from as far away as Invercargill, Blenheim and Hokitika.
Their vehicles ranged from a 2010 RS Ford Focus to vintage racers.
