Depending on where you live in the Auckland region you could be paying as much as 64c more a litre than motorists stocking up at one of the Super City's cheapest service stations.
As national petrol prices reached new heights this week, hitting $2.30 a litre, the Herald compared the going rate among the super city's petrol stations this morning.
The price of 91 has risen by nearly 20c a litre since January when it was $2.12 a litre and climbed past the previous high of 2013 when it was $2.27 a litre.
Using the fuel price compare app Gaspy and by calling into service stations directly we found the price of 91 cost as little as $1.87 or as much as $2.51 a litre across 144 stores stretching from Bombay to Wellsford.
This included Waiheke Island but not Great Barrier, where petrol sells for $3.11 a litre.
The survey was unscientific and did not include every petrol station, in some cases because staff said they were not allowed to read out prices over the phone.
Nationally, petrol prices varied by more than a dollar this week, with 91 selling for just $1.93 at one Rotorua service station, and a whopping $3.11 on Great Barrier Island yesterday.
The price difference in Auckland today wasn't quite so pronounced, and most places we checked were selling 91 between $1.99 and $2.20 a litre.
Waiheke still has the region's most expensive petrol excluding Great Barrier, with 91 selling for $2.51 a litre at both the local BP and Z.
This was 64c more than Gull stations in Titirangi and Millwater, selling petrol at $1.87 today as part of a promotion docking 12c off the price of a litre of fuel until Friday lunchtime.
Gull stations in Wellsford, Papakura, Wiri, Papatoetoe, Takanini and Onehunga were also selling 91 at cut prices only a few cents more than Titirangi and Millwater.
General manager Dave Bodger said the promotion was bringing in double the usual number of customers for a Thursday.
"People are most excited."
On the mainland the BP in Bombay wasn't far behind Waiheke, selling for 91 $2.41 a litre when the Herald called.
Bombay was much dearer than its northern Super City boundary counterpart Wellsford whose 91 was $1.94 at Caltex and Mobil and slightly less at Gull.
Overall it seemed the closer a suburb was to the city centre the dearer its fuel, despite a greater concentration of service stations for drivers to choose from.
The AA's Mark Stockdale credited this difference to the "Gull effect", the phenomenon whereby prices stay lower in areas with cheap suppliers like Gull.
Because Gull was a discount supplier it favoured setting up shop in lower-cost parts of the city and avoided areas with higher rent, Stockdale said.
"If you're a low-cost brand you need to operate in low-cost areas."
Generally, petrol prices north and south of the Super City's boundaries hovered between just under $2 and $2.15 a litre.
In South Auckland, 14 petrol stations across Otara, Otahuhu, Takanini, Onehunga, Papakura, Papatoetoe and Manurewa were selling 91 for less than $2 a litre, making up nearly half of the 31 petrol stations we found selling under that threshold overall.
Meanwhile, petrol stations in inner city suburbs like Ponsonby, Newmarket, Mt Eden, Pt Chevalier and Herne Bay were all selling 91 between $2.20 and $2.24 a litre.
Across the Harbour Bridge and beyond in Silverdale, Whangaparaoa and Matakana, most petrol stations were selling 91 for $2.17 or $2.18 a litre.
In nearby Orewa prices were much cheaper - $2.03 at Caltex and $1.87 at Gull.
Mobil was the most likely company other than Gull to sell 91 for less than $2 a litre, with nine of the 31 Mobil stores we checked selling for $1.99 or under.