The course finished spectacularly with a 55-degree rocky climb and Nield moved up to 11th place.
The third and final day was more than 150km of advanced hill climbs, with the final 6km never attempted before and recommended only for the "super fit, super strong or super stupid", Owen said.
This year's race attracted many of the world's best riders from New Zealand, Australia, Germany, the UK and South Africa.
Graham Jarvis, of Britain, finished first, pushing New Zealand's Chris Birch, who had won for the previous three years, into second place. Other Kiwis included Michael Skinner 13th, Karl Power 15th, Phillip Cheater 29th and Chris Power 33rd.
Nield left in mid-October to train in South Africa for the event. Owen said he had worked so hard to prepare for the race he deserved his top-10 placing.
He had competed since he was nine and took out his second national under-200cc title at the 2011 New Zealand Enduro Championships, a series of six events at farms and forests around Northland.
He had also competed in Australia's annual four-day Enduro Championship, winning a silver medal in 2006 and gold in 2007.
The Northland rider arrives back in New Zealand today.