Police and retailers have told the BBC they are seeing an increase in thefts of fuel from forecourts as petrol prices hit record levels.
As well as people driving off without paying, there is also a rise in motorists filling up and then claiming they cannot pay.
West Midlands police have devised guidelines to help station attendants spot potential "bilkers".
Retailers are joining a debt recovery scheme to reclaim the unpaid money.
In the Small Heath district of Birmingham, Pc Lee Woolman says that each week he has to recover CCTV images of fuel thefts from at least one of the three forecourts in his patch.
He has devised a series of guidelines for retailers which he hopes will reduce theft. "On a lot of occasions, people drive their cars in the wrong way, so the vehicles will be facing the wrong way," he says.
"We quite often get people with hats on covering their faces, hoodies, bicycle helmets, and we encourage staff to get on the Tannoy, make sure they are taken off before they load up with fuel."
At one forecourt where some fuel had recently been stolen, an old police car had been parked.
Called a bilking car, it is intended to deter potential thieves by giving the impression that officers are nearby.
Petrol prices rose by 10% in the year to December, and have risen 6p a litre in the past month.
A 2007 study from Australia found that for every 10c (about 6p) rise in a litre of petrol there were 120 extra incidents of theft.
Ch Insp Matt Markham from West Midlands police says: "Anecdotally, we can support the conclusion."
At the Three Elm service station in Kent, the problem is not so much motorists driving off without paying as customers saying they cannot pay.
"We have seen a huge increase," says station manager Sonia Dellow. "We have a lot of problems with people saying they have forgotten their wallets.
"They will fill in a no-money form which then they don't come back and pay," she adds. "We've had a dozen this month - it's usually about one per week."
The British Oil Security Syndicate, which aims to stop forecourt crime, has created a debt recovery scheme in an attempt to get the money back from customers who do not return to pay their fuel bills.
They say the scheme has been successful, but they fear the number of such crimes will increase as fuel becomes increasingly expensive.
You can hear Michael Buchanan's full report on the rise in petrol prices in The Report on BBC Radio 4 on Thursday 27 January at 2000 GMT. You can also listen on the iPlayer or subscribe to the podcast.