Z Energy has changed its petrol pricing strategy to more aggressively match localised competitors.
The petrol station operator's net profit for the six months ended September fell 61 percent to 22 million.
Some of the factors driving that fall including the well-publicised problems at Refining New Zealand and unrealised foreign exchange losses were beyond the company's control.
However, the volume of Z's petrol sales fell 4 percent drop in the six months despite industry volumes rising 1 percent.
Listen to Z Energy chief executive Mike Bennetts on Business News