Oil-rich City boasts some of the nation's most promising players - including four members of Gary van Egmond's Young Socceroos side - but it was the Suns who looked like the young talent factory in dishing out a 5-3 masterclass.
In less than four minutes, two 18-year-old Suns had combined to find their side the lead, with Fraser Gosstray smashing one home in his first senior start thanks to an Alou Kuol assist.
Soon after, Kuol made it 2-0 with a neat bottom-corner finish, but City found two goals in five minutes to level the scores, with former Sun and Cobram product Gianluca Ianucci getting on the end of a counter-attacking move for the first of the goals.
Seconds after the Citizens had leveled things up, Kuol struck again with another lethal finish, and Vani Shamoon made it 4-2 on 33 minutes.
City pulled one back through Stefan Colakovski early in the second half, but Jordan Montagner headed home a corner on 80 minutes to put the game to bed.
Nine points clear of seventh-ranked City, the Suns are more than likely to avoid relegation to the state's third tier, a fact that greatly pleased coach Craig Carley.
"We were under no illusions it was a massive six-pointer, if we lost that Melbourne City would have been right on our tail, but the win means we've got some breathing room," Carley said.
"We've almost cemented our spot in NPL2, and that was certainly the aim at the start of the season.
"The boys knew the level of concentration needed against a side like City and to be fair they all worked hard all week. We knew exactly how they'd set up and I thought we nullified them quite well.
"I was disappointed with the goals we conceded because they were basically three mistakes, but to score five, I'll definitely take the 5-3 win."
From what has been an up-and-down season, the Suns would certainly take a top six finish, particularly given they were five points back from safety just 12 games ago.
"I think we fully deserve to be in the division," Carley said.
"We've dropped nine points from goals we've conceded in the last five minutes of games and that would put us second on the table.
"We spoke to people from Melbourne at the weekend and they said they'd written us off earlier in the season and they thought we had no chance of staying up. It's pleasing to prove a point in that regard and it looks like we'll be the only regional team in the NPL2."
Earlier in the night, the Suns' under-20s proved no match for Melbourne City, beaten 4-0.
The Suns were 2-0 down at half-time and conceded another pair in the second half, with Maxwell Branov netting a hat-trick.
They are eighth on the table, having lost five consecutive games.Â
