Why petrol prices rise faster than they fall

It is not your imagination. New Zealand research found that petrol price increases reach the pump faster than decreases, although the difference is temporary.

What the New Zealand research found

The Commerce Commission compared changes in fuel company costs with national pump prices for Petrol 91 and Petrol 95.

During the first week after costs changed, about 70% to 80% of an increase had reached pump prices. Only about 30% of a decrease had been passed through over the same period. The difference could last for up to two weeks.

The Commission estimated that drivers would save about $15 million a year if prices fell as quickly as they rose. Its fuel price report also found no evidence that cost decreases were never passed through. The issue was the speed, not a permanent refusal to lower prices.

Why can a fall take longer?

The speed varies with local competition, retailer behaviour and how actively drivers look for a cheaper station. A station can also be part way through adjusting its margin after an earlier cost rise.

This does not mean every station follows the same pattern. Local prices can move at different times, and a national average smooths those differences together.

Why are petrol prices still high when oil has fallen?

Crude oil is only one part of a litre of petrol. Refined fuel costs, the New Zealand dollar, shipping, taxes and retail margins also matter. A fall in one part may be offset by a rise in another.

There is also a delay between a change in international costs and the price on a New Zealand pump sign. Our guide to how fuel prices are set explains those parts without assuming every oil headline should appear immediately at the pump.

What this means when you need to fill

A falling market does not guarantee that tomorrow's station price will be lower. It does mean there may still be a reduction working its way through over the next week or two.

That delay is exactly the period covered by Fill or Wait. The forecast cannot guarantee a fall, but it can help you decide whether waiting is worth considering.

Check the fuel price forecast for next week and the week after →

Commerce Commission findings published in June 2024 and checked again on 2 October 2026.