Oceana Gold mobile maintenance manager Cliff Webb, of Palmerston, said five Caterpillar 789D mining trucks had recently been bought to work at the Macraes gold mine.
The trucks were bought to replace five due to be retired and used for parts.
The trucks being replaced had worked for 75,000 hours.
"When they get to that age, they get less reliable.''
The mine had a fleet of 18 Caterpillar mine trucks.
A new truck cost about $4.5 million but the five trucks were bought at a reduced price because the first owner, a mining contract company in Chile, had bought them in 2013 but never used them.
"They never won any work for them and subsequently sold them ... They were sold at current used-market value so it was a no-brainer, really.''
Mr Webb would not "divulge'' the amount paid for the trucks.
Each truck arrived in two pieces - the full chassis and the deck.
A feature of the new trucks not found on the retired trucks was a radar system to warn the operator if another vehicle was nearby.
The compliance work to meet site specifications, such as installing a larger fuel tank, had begun, he said.
He expected the trucks to be working in about three weeks.
A truck could work carting rock, rock spoil and gold for up to 20 hours a day, every day of the year, if required.
Caterpillar 789D
•Cost $4.5million new.
•Weighs 140 tonnes.
•Can carry 200 tonnes of rock.
•V16 engine, 2100 horsepower.
•About 7m wide and 6.5m high.
•Each tyre costs $50,000.
