Reynolds drove to his third win of the season after a late pass on eventual championship leader Scott McLaughlin on the streets of Newcastle.
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The Shell V-Power Racing team dropped McLaughlin out in front of Reynolds as they covered off title rival Shane van Gisbergen in the stops, with McLaughlin then effectively holding the race lead until Lap 91.
A late charge from Reynolds saw McLaughlin offer no resistance, allowing Reynolds through to take the race win.
Having crossed the line third on Saturday, Reynolds was promoted to second following van Gisbergen's post-race penalty for a pit stop infringement.
Alongside Reynolds' three wins, the team banked six other podium results that left the team with a best-ever finish of fourth in the team's championship, having entered the series back in 2013.
“I'm really happy to finish the year on a high, we had a perfect day with pole and the win,” said Reynolds.
“We were faultless again today and we minimised our mistakes, had great stops, a great car and strategy and that got us the win.
“Our year has been amazing; we've had nine podiums; a couple wins and a few poles,” he added.
“Since I've joined the team we have just got better and better.
“We are the same crew I started with in 2016 and we've worked hard, and we just keep going better, I'm so proud of everyone.”
Erebus ended the year fourth in the teams' championship, its best ever result after finishing seventh last year.
Fifth for Reynolds in the drivers' competition is his best since finishing third for Rod Nash in 2015, and a two-place improvement from last year.
“This year we started really well, we were second in the championship for a long time,” he said.
“What really hurt us were the Saturday races.
“On the Sunday we learned what we had to do with the car for the longer race and we always capitalised on the Sunday much more than Saturday.
“That's what kind of hurt us.”