Z Energy dropped its retail fuel prices on Monday morning.
Ninety-one octane petrol is now four cents cheaper at $2.15. 9 per litre and diesel is lower by three cents at $1.53.9 per litre.
Z Energy says steadily easing global fuel prices and a stabilising New Zealand dollar are behind the reductions.
The company also says it needs to make more profit so it can reinvest in fuel storage.
Its net profit margin on fuel sales was 2.1 cents per litre last financial year.
Retail general manager Mark Forsyth says that margin has been about four cents more recently.
He says Z is just recovering years of under-investment in New Zealand storage infrastructure.
Mr Forsyth says higher margins provide the confidence Z needs to commit $50 million of investment in bulk storage infrastructure.