Z Energy, BP, Mobil and Gull have lowered the price of petrol by 3 cents a litre on Friday.
The cuts follow a fall in international fuel prices.
BP spokesperson Jonty Mills says international market conditions remain volatile, but it is pleased to be able to make these cuts before the weekend.
Diesel is also down by 2c a litre at Z Energy and 3c per litre at the other companies.
