Motorists could end up forking out hundreds of pounds in fuel this summer as millions prepare to embark on holidays up and down the country.
New data from the AA has revealed that drivers could end up spending as much as £1.70 per litre when filling up on the motorway over the coming weeks.
Research from motorway service stations around the UK found that a litre of petrol on the M74 between Junctions 4 and 6 could cost 170.9p, while costs of 168.9p could be seen on the M6 between Junctions 14 and 15.
It comes as nationwide petrol and diesel prices have jumped over the last month, with petrol rising from 132.1p to 138.2p.
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|Motorists could be slapped with huge costs depending on where they fill up
Diesel drivers have seen a similar price hike from 134.6p to almost £1.42 per litre, as a result of global oil instability, stemming from the conflict between Israel and Iran.
However, drivers can expect to pay far more on the motorway when on their travels, with motorway service stations averaging 155.7p for petrol and 164.4p for diesel.
In comparison, major A-roads are charging just over 140p for petrol and 147.6p for diesel, with drivers encouraged to shop around, rather than settling for their nearest forecourt.
Drivers are consistently encouraged to fill up before they head on long journeys, not only to reduce the risk of a breakdown, but also to save on fuel costs.
PA | Drivers are encouraged to avoid filling up at motorway petrol stations
Since motorway service stations have a captive audience, retailers can charge as much as they like, since they know drivers have no other choice but to fill up.
Edmund King, president of the AA, said it was not a surprise that holidaymakers are increasingly turning their backs on buying fuel at motorway service stations.
He added: "Even with the extra costs of providing a 24-hour service, free parking and facilities and staffing, charging 20p to 30p a litre above the UK average pump price or £10 to £15 a tank more to fill up on a motorway is frankly outrageous."
Clear differences in price can be seen along popular routes up and down the country, including a 26p saving on petrol and diesel on A-roads compared to the motorway when travelling between London and Exeter.
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More modest savings can be seen between North-South routes, with drivers able to save around 13p for petrol and diesel on the A1M/A1 compared to the M1/M6 average.
Drivers travelling in and out of Wales can also save, with prices falling at least 13p for petrol and diesel when driving on the A55 rather than the M4.
King added: "While there is a danger that pricing at so many motorway service areas tars them all with the same brush, pump price transparency courtesy of the CMA voluntary scheme is revealing the better if not bargain-priced fuel stations along popular holiday routes.
"Mobile services like the AA App, now no longer hindered by the search restrictions of old, allow users to trace a route and locate the previously hidden cheaper fuel stations along it or just off the junctions."
PA | Filling stations found at motorway services are around 20p per litre more expensive
Despite the general trend of motorways being more expensive, the AA data found that cheaper fuel costs can be found along busier routes, including Lancaster (J32-33) on the M6 and Oval (J16) on the M1.
Surprisingly, the M25 at South Mimms (J23) is around 10p cheaper for fuel than other motorways, despite being a popular route for Britons.
King concluded: "Savings on A-road holiday routes stand out in particular. However, there is the likelihood of slower traffic at peak times and many cheaper fuel stations will not operate late at night.
"It's a gamble, but it may well pay off if a vacation trip cannot be done in one hop."