The German started second on the grid but eventually finished ahead of his teammate Mark Webber for his third win in a row.
"I'm very pleased," he said. "It's fantastic. The foundation was to have a good start.
"I wasn't sure because I was starting on the dirty side but I had a good launch and managed to get past Mark. But it wasn't over, it's a long way and even in seventh gear I could hear Mark coming.
"We were a bit worried about the front wheel because we've seen a lot of people locking up and overshooting the apexes. The team have been flat out on the car since Japan and that's what we need."
"I'm looking forward to next couple of races," said the 25-year-old. "A lot can happen but we need to focus on ourselves and go from there."
There are four races remaining this season.