BP, Shell, Mobil and Caltex all cut their retail petrol prices by 3 cents per litre on Monday morning.
The price of 91 octane is now $2.03.9 cents per litre.
BP New Zealand managing director Mike McGuinness says the move is mainly driven by weakening product prices overseas.
Mr McGuinness says 91 octane was priced at $1.97.9 per litre at the start of the year. It reached a high of $2.21.9 per litre in May.
Brent crude oil was trading at $US107.76 US per barrel earlier on Monday.