Fuel importers have been making bigger margins recently, and there is a warning it could dent the impact of falling oil prices on New Zealand motorists.

Data from the Ministry of Business, Innovation and Employment (MBIE) showed the fuel importer margin was about 15 percent to 16 percent of fuel prices through the start of 2025 - higher than the long-term average over the past 20 years of 11%.

Infometrics chief executive Brad Olsen said as fuel prices rose, the level of margins would tend to rise too.

"Using a 12-week moving average, the petrol importer margin has been above 15 percent between the end of September 2024 and mid-November 2024, and since the start of January 2025.

It's the first time the petrol importer margin has increased to above 15% on this three-month average measure since July 2020.

"The rise in the fuel importer margin proportion highlights that fuel importers are making a higher margin on fuel at present - and the trend there is a higher margin than has been seen in recent years.

There's no immediate and simple explanation for why those margins have increased."

Price monitor Gaspy said prices had fallen from a nationwide peak of $2.76 a litre for 91 in January to $2.70 on Tuesday.

Olsen said the more recent drop in prices was driven by worries about economic growth globally because of the threat of tariffs and uncertainty about US President Donald Trump.

"Markets are worried about economic growth, and lower global growth would require less oil. That lower expected demand has pushed oil prices a bit lower.

"Rising expectations of the start of talks to end the Russian invasion of Ukraine has also raised expectations that, if a deal is concluded, Russian oil sanctions might be withdrawn, adding in more anticipation of supply.

"However, if the importer margin persists at a higher proportion - like recently - there might be less pass-through of lower oil prices into prices at the pump.

"There's no clear justification for why importer margins have increased."

A spokesperson for Z Energy said it was committed to ensuring customers had a fair deal at the pump.

"Z acknowledges [MBIE's] fuel importer margin data and supports sharing information of this nature to provide consumers and regulators with assurances that fuel importers are delivering fair and reasonable pricing in a highly volatile operating environment.

"However, Z does not believe MBIE's data provides accurate insights to actual operating profits or market competition for fuel importers.

"We have raised our concerns about the accuracy of this data directly with MBIE, including the price sampling methods used, the costs of discounts available to customers, and the impact of cost inflation over time. We remain committed to working with MBIE on this matter."

Gaspy spokesman Mike Newton said the drop in petrol prices in recent weeks tracked an increase in the New Zealand dollar after a sharp fall in January.

"As long as the New Zealand dollar continues to rally it'll probably continue either plateauing or slightly decreasing."

He said people could save money on their fuel by watching for discount days. He said Gull was doing one weekly, and other stations nearby would often match it.

Sign up for Ngā Pitopito Kōrero, a daily newsletter curated by our editors and delivered straight to your inbox every weekday.