Motorists are forking out almost £150million every year for repairs after putting the wrong fuel in their cars.
Around 300,000 vehicles are misfuelled every year in the UK according to car retailer Halfords, at an average rate of once every two minutes.
The most common reason for the mistake comes from motorists who have switched from petrol to diesel-fuelled cars and simply not realised.
As a result, it is newer cars that are more likely to fall foul of the mistake (those under four years old) with incidents peaking in both March and September when new registrations are released.
Unfortunate motorists are faced with hefty bills, ranging from £500 to colossal £3,000 for repairs.
The size of the nozzles used for petrol and diesel is said to contribute to the problem.
Paul McClenaghan from Halfords said: "Putting petrol in diesel vehicles is unfortunately very easily done as the unleaded nozzle on the pump fits into the filler neck of the diesel vehicle without any problems.
"It only takes a momentary distraction or lapse in concentration and the consequences are often costly. The diesel nozzle has a larger diameter so it is more difficult to do the other way around- although some people have managed it!"
There is some good news for motorists, however, as fuel prices could be set to fall by as much as 4p/l over the coming weeks, says the AA.
Their October report says due to demand in the US falling, the increase in fuel prices seen by motorists in September should be balanced out in the coming weeks.
Prices of fuel have already dropped by 1.26p a litre for petrol and 0.86p a litre for diesel.