The summer of low petrol prices looks to be over.

The chances of a long spell of low petrol prices look slim, as motorists face paying up to 40c more a litre in the coming months.

Automobile Association senior policy analyst Mark Stockdale said that, if the cycle held from the past two years, this week's 6c rise signalled prices were heading back up.

"What we're seeing is almost exactly a repeat of what happened this time last year."

In February last year, the average price for 91-octane petrol bottomed out at $1.73 a litre. By July, it had bounced back to $2.12.

With prices already heading upwards, "that appears to be what we're seeing", he said.

Price changes had nothing to do with domestic demand, but were tied to international petrol prices, which had increased by $5 a barrel in the past week, he said.

Professor Christoph Schumacher of Massey University said the saying that petrol prices "rise like rockets but fall like feathers" seemed to hold true.

Higher prices not only affected consumers directly at the pump, but forced up costs for transport for all businesses.

On the streets of Wellington on Tuesday, motorist Christine Caughey said fuel increases would "absolutely" have an impact on her wallet, despite the fact she used public transport when she could.

"Having to fill your car up with $110 rather than $70, $80, there's a huge saving lost."

She was visiting Wellington from Auckland, and was impressed by the number of people walking, riding and using public transport.

Without decent public transport, she said, people were held hostage by petrol price increases, particularly low earners.

She believed more money from petrol taxes should be used to improve public transport.

Vaughan Hayton said fuel increases weren't necessarily a bad thing as it seemed to cut the amount of traffic on motorways. "The higher the petrol prices go, the traffic eases up. So I'm probably voting for higher prices."

However, Stockdale said the evidence showed that people did not drive less when prices went up. Instead they spent less on other things, forgoing "buying coffees and going to the movies".

PUMPING IT UP

The annual national average pump price for 91-octane has trended up since 2008, but the increase has slowed over the past two years.

At the same time, international refined petrol prices have plummeted from $135.47 a barrel in March 2014 to $64 at the start of March this year.

AA's Mark Stockdale said the low price was offset by a very weak New Zealand dollar, which was at its lowest March point against the US dollar since 2009.

2008: 184.11c

2009: 161.54c

2010: 178.89c

2011: 208.22c

2012: 213.60c

2013: 215.32c

2014: 215.93c

2015: 197.98c

- Data supplied by the Automobile Association.