Wellington, Aug 17 NZPA - Two petrol companies have today dropped their petrol prices.

Greenstone, the owner and operator of Shell service stations, made the 2 cent drop to 175.9c per litre of 91 octane, citing a drop in the cost of fuel on the international market.

BP also dropped its petrol prices to 175.9c, saying the lower cost of fuel internationally outweighed a weaker New Zealand dollar.

The price of diesel remained unchanged.