If you’ve been road tripping around the country lately, you might have noticed something unusual.

While no one likes forking out for petrol to fill up their vehicles, the amount you have to pay can vary a lot, depending on where you are.

Gaspy data shows that the average price for 91 on Monday was $2.66 a litre, down 2.5 per cent on the previous 28 days.Diesel was $2.07 and 95 $2.86.

But the cheapest gas stations, Pak’nSave in Rotorua and New World Westend, were selling 91 for $2.42.

Some of the priciest petrol is usually found on places such as Waiheke Island and Stewart Island. On Waiheke 91 was $3.91 on Monday, according to Gaspy.

Terry Collins, AA’s principal policy adviser for motoring affairs, says he noticed the prices moving when he travelled around the country recently.

“I was surprised where some of the prices changed…. I filled up accordingly along the way, rather than waiting to get to Auckland where you’d pay a regional fuel tax I fuelled up at Putaruru which seemed the cheapest option.”

So what drives the difference?

Competition

Terry says competition was the biggest driver of price.

“One of the prime examples of that is when the Commerce Commission does its annual survey it often finds the likes of Hamilton have got the cheapest fuel around. Around the Te Rapa area, there’s a high density of New World and small independents, that competition keeps the price down.

“Both are around 100km away from a port, 103km to Tauranga and 110km to Auckland but transportation isn’t a factor there.”

He says in Wellington, the sharpest prices were around Petone.

“Probably the sharpest offer is always Petone Pak’nSave, around the corner you’ve got Waitomo, Gull, a whole variety of low-cost operators, collectively that competition keeps the price down.”

Distance to delivery

But in some parts of the country, the cost of getting fuel to a petrol station is a factor.

Terry says in Whitianga and the Coromandel area, the cost of delivery could affect prices.

That can also be seen in areas such as Waiheke Island and the West Coast of the South Island.

Who owns the petrol station?

Terry says the owner of a petrol station would affect the prices it charged.

“If they are company-owned they tend to set their prices every week across the company. If they are independent, they have more choice what they sell for.

“There’s a small one owned by a community group near Atiamuri that consistently has some of the cheapest fuel around, that’s the tie to the community keeping it down.

“Sometimes you see in small rural places that you think would be higher but the connection to the community means the prices are a bit sharper.”

Smaller, no-frills operators tend to offer lower prices.

Fuel tax

Auckland has had a 10 cent per litre regional fuel tax since 2018, although National has indicated it will scrap this. This makes filling up within Auckland more expensive than other parts of the country.

Terry says overall, the price of fuel was driven by the price of crude oil, refining costs, transportation costs and the exchange rate.

Then there are local taxes, company margins and profits and GST added.

“It’s a cost-plus model.”

Oil prices are down significantly from their peaks in late September but shipping costs have nearly doubled this month due to attacks on shipping in the Red Sea.

Susan Edmunds/Stuff.