Nico Rosberg made it four wins in five races with a comfortable success at a cloudy, and briefly damp, Suzuka on Sunday.
A strong start set pole-sitter the German up as he won from Red Bull’s Max Verstappen and team-mate Lewis Hamilton.
Championship rival Lewis Hamilton – winner in Japan the previous two years – was left to rue a slow start that saw him slip from second to eighth.
But his excellent recovery, and late battle with Verstappen, could yet prove crucial in the title fight.
With four races remaining, Rosberg has extended his lead to 33 points over Hamilton.
1. Nico Rosberg (Mercedes) 313
2. Lewis Hamilton (Mercedes) 280 (-33)
3. Daniel Ricciardo (Red Bull) 212 (-101)
4. Kimi Raikkonen (Ferrari) 170 (-143)
5. Max Verstappen (Red Bull) 165 (-148)
1. Mercedes 593
2. Red Bull 385 (-208)
3. Ferrari 335 (-258)
4. Force India 134 (-459)
5. Williams 124 (-469)
Time is running out for Hamilton to catch Rosberg, and he will get another chance at the United States Grand Prix in a fortnight’s time.