Maitland had the state's most expensive average unleaded petrol price last week, jumping almost 20c/l from the previous seven-day period.
According to the latest pricing data released by NRMA on Monday, the average cost of unleaded fuel at the bowser was 153.2c/l in Maitland for the week ending September 22.
Maitland's 18.5c/l increase from the previous week was massive compared to price rises elsewhere across the state, with Bathurst recording the next highest jump at 6.2c/l.
Newcastle's seven-day average was 150.7c/l - though that was the result of a 1.7c/l increase from the previous week.
The Central Coast posted a 147.6c/l average - a drop of more than 4c/l.
In the valley, Muswellbrook's average was 139.7c/l, while Singleton's was 141.6c/l.
The state's cheapest average unleaded petrol was in Gunnedah, according to the data, where the fuel cost 136.4c/l.
Bega, in south-eastern NSW, trailed Maitland by only 0.1c/l to be the state's second most expensive.
"Maitland's petrol prices were relatively low compared with other similar regional markets over the past several weeks," NRMA spokesperson Rebecca Page told the Newcastle Herald.
"So it was only a matter of time before they were brought into line, which explains this sharp increase.
"One point of difference in Maitland is that there are only eight service stations, so when there is a significant price change at any of those outlets, there is a dramatic impact on the town's average.
"We're expecting prices to keep rising slightly in the Newcastle and Hunter Region over the next week or so, so our advice at the NRMA is to stay informed and shop around for fairer prices."
According to NRMA's latest report, the average price of Mogas 95 - which the motoring group said was the key petrol benchmark for this country - increased by 7.9c/l in Australian terms last week.
It said this meant the average price of Mogas 95 had jumped by 19.5 per cent in the past fortnight.
Ms Page said it was "so important" for motorists to check prices to avoid being "stung at the bowser".
"There can be a difference of up to 15c/l between servos within short distance of each other and we know that for an average family car that fills up once a week, that can be upwards of $700 a year either spent at the bowser or put towards family spending," she said.
