Will petrol prices go down?

Two signals, both measured

The first is the gap between what motorists pay and what retailers pay at the terminal gate. Pump prices are sticky: when the gate jumps, retailers absorb part of it for a week or two and the gap narrows. Over the 20 weeks with both figures since May 2026, the 91 gap averaged 13.4c. In 6 weeks it fell below 8.9c, and the national pump average rose the following week in 5 of them. In 5 weeks it was wider than 17.9c, and the pump fell the week after in 4.

The second is MBIE's own cost series, which goes back to 2004. In 293 weeks the import cost of 91 moved by 3c or more; the pump price moved the same way the following week 88% of the time. For diesel the hit rate is 84% over 295 weeks. This week the 91 import cost moved −1.1c and diesel −16.9c.

Neither is a forecast of where crude oil or the exchange rate goes next. They describe how New Zealand pump prices catch up with costs that are already known, which is what most people asking whether prices will drop want to find out.

Diesel and what to watch

For diesel the gap was 0.2c in the week to 25 September 2026 against an average of 26.1c. BP moved its diesel gate by +5.7c on 6 October 2026; Z's 7 October 2026 list moved diesel +0.9c.

BP publishes a new gate list whenever its price changes, so it is the earliest public sign. Z publishes on Wednesdays and MBIE's weekly averages follow a few days later. Today's figures are on today's price board; how the margin behaves when costs move is on MBIE's importer margin series.