The heat is on Mark Winterbottom to retain his V8 Supercars championship lead, after Ford teammate Chaz Mostert closed the gap with two wins in three races at Sydney Motorsport Park.

The young gun closed out the final round before the all-important endurance series with victory in Sunday’s rain-hit and shortened 50-lap feature.

He crossed the line 7.6 seconds ahead of the Holdens of Fabian Coulthard and Jason Bright.

It followed Mostert’s two pole positions, race win and podium on Saturday, which pushed him up from third to second on the driver’s standings.

He now sits just 174 points behind Winterbottom, who qualified in 12th and finished a lowly 16th.

“It all came down to strategy,” said 23-year-old Mostert.

“Obviously the rain played a big part and the car was pretty good in the rain.

“A big thanks to the team.”

Holden veteran Craig Lowndes, who came into the weekend hot on Winterbottom’s tail but is now third overall, came in 10th.

Teammate and six-time champion Jamie Whincup couldn’t build on his drought-breaking win and podium on Saturday, managing only 14th place.

Volvo’s Scott McLaughlin started on pole but had to tussle with the Ford of David Reynolds for the lead on the opening lap.

McLaughlin held on, but his effort was undone by a safety car just as the second lap got underway – triggered by a collision between his teammate David Wall and Nissan’s Todd Kelly.

The entire field headed straight for the pitlane to top up with fuel and mix up their tyres.

Mostert came out in front, ahead of Reynolds, as each team’s strategies began to play out.

But they all went out the window when the heavens opened on lap 25.

Dale Wood was the first casualty, sliding his Commodore on the wet track and beaching it in the gravel.

It prompted another safety car and a slew of manic pitstops.

Mostert again emerged in front and managed to stay there for the remainder of the race, which was cut by two laps due to broadcast and scheduling time restrictions.

The championship next heads to Sandown from September 11, marking the beginning of the endurance series.

The Bathurst 1000 and Gold Coast 600 follow on October 11 and 25.