Biggs likewise had a clean sheet in the afternoon round, to go with conceding only 40 penalty points in the morning, which added up to an excellent 75.25 final total once the timed courses were added in.
"He certainly didn't go easy on me just because I had a broken leg," said Auret.
"We just gave the afternoon everything we had. Just threw everything at the hills.
"When we zeroed it we thought, 'well, good luck to him', but then we came back and saw he had as well.
"He was slightly faster than me on the speed.
"There was nothing in it. We could see each other in the distance. We were both attacking."
Although Biggs no longer has the services of his co-driver brother Jarred, who finished fourth on Saturday in his own truck, the champ has secured the very experienced Phil Walton – the Manukau driver who had been leading the 2017-18 points table in the early stages.
In the rest of the 54 truck field, Hamilton's Russell Luders finished third in D-Class and overall, while Taranaki's Rowan Huckstep rounded out the Top 5.
"I really enjoyed the day, thrilled with the result," said Auret.
"[Biggs] knows we're there. But he knows we've got a long way to go."
In the six-round series, drivers drop their worst result from their final tally, but Auret and Barnes have used up their spare by missing Upper Hutt.
"We've got no backstop, we have to have four more good ones or we're stuffed," Auret said.
"There's 20 trucks that can win it on the day, and if you don't have a good day, you can get shunted down."
Turakina's former national champion Dan Cowper could testify to that, as a couple of expensive obstacles where he conceded 60 out of a possible 100 points really cost him in the afternoon session.
Coming into the round sitting fourth place after Upper Hutt, Cowper finished ninth in D-Class and 10th overall.
"The two 60's right at the end of the day. Just the timing of when I hit those two courses," he said.
Cowper had observed the tyre marks left by Auret on the No12 obstacle, but opted to try a different route upwards.
"I kicked myself for not going where he went.
"Then you see the competition do it after you and think, 'aw, jeez, why didn't I'?"
The next course was now thick with mud after 50 trucks had driven over it, and although Cowper stuck the truck in top gear, they bellied out.
The veteran truck-builder said he had got the feeling early in the day that they were in for a tough time given their scheduled rotation through the obstacles, and he decided to protect the truck as much as possible so to not spend Christmas fixing it.
"It was one where we knew we had to get through in one piece.
"You had to pick and choose the rushes you take over the course of the day."
The third round will be hosted by the South Waikato 4WD Club on January 19.
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There is added incentive to the drivers in the national series to have a good campaign as it relates to Dan Cowper's private Suzuki Extreme Challenge, which will be held for the fifth time on April 28 at his Turakina farm.
The popular event, which is screened on TV3, previously saw drivers take part at Cowper's invitation.
This year, he has announced the Top 10 finishers in the national series will qualify for the challenge.
The event has been won twice by current national champion Scott Biggs, and twice by Tauranga's Andrew Garner, who is not doing the national series.
