Do petrol prices fall as fast as they rise?

Z Energy says new research backs up its claim that petrol prices rise and fall at the same speed.

A new report claims to have disproved a well established urban myth that petrol companies are quick to raise petrol prices, but slow to drop them when prices fall.

Z Energy has today released updated research from the New Zealand Institute of Economic Research (NZIER), which showed petrol prices fall as quickly as they rise at the pump, as oil prices increase and decrease.

NZIER's initial analysis, carried out in 2013, was prompted by lasting complaints that petrol companies are quick to raise petrol prices at the pump, but then conspire to drop prices slowly when international oil prices fall.

The update of the 2013 report was funded by Z Energy, who wanted to know whether the findings from 2013 remained relevant today.

Spokesman for Z Energy, Jonathan Hill said it was a "routine accusation" of the industry that prices were quick to go up and slow to come down.

"The NZIER did that [initial] piece of work in 2013 and we just thought, especially given the volatility that we've seen in the markets over the last six months in particular, that it was timely to update that.

"I think given how widespread the view has been it is a useful point to keep proving to consumers."

Although today's report did not differ from the initial report in 2013, in terms of petrol prices rising and falling at the same speed, it found that price change pass-through had become more rapid in the past three years.

"This means both oil price reductions and oil price increases end up in retail prices more quickly than they used to," the report said.

"From a consumer perspective these dynamics are positive. These results suggest that competition has become more robust.

Automobile Association (AA) analyst Mark Stockdale said the findings of the report came as no surprise, and were reassuring for the public.

"There has been various independent experts who have monitored the retail fuel market and have all concluded the same things, as the AA has concluded, and that is that prices at the pump fall as quickly as they rise.

"The latest report confirms our understanding. That is reassuring for the public because what that means is that the public can have confidence that New Zealand does have a competitive retail fuel market," Mr Stockdale said.

"A sign of a competitive market is when they do adjust their prices promptly in relation to changing commodity prices, and that's what you're going to expect to see in the competitive market."

Consumer NZ chief executive Sue Chetwin said while the findings of the report reflected findings of other independent reports, she would like to see by how much prices actually dropped by.

However, Mr Hill said the report focused on whether or not prices were mirrored by the commodity price, and not on how much they dropped by.

"The extent to which prices rise and fall depends on the movements on the commodity price."

General manager for Gull, Dave Bodger said he was aware of the report, and although he had not yet read it, said the findings sounded accurate.

"I think petrol prices do go up and down at a level rate, because there is a lot of competition in New Zealand. I think that independents such as Gull adding that competition really put the ginger on to oil majors to make sure petrol prices do drop at the right time."

Read the NZIER report here: