RAC says oil prices are 'cooling', so rises may be short-lived.

Last month saw the highest increase in average petrol prices for at least 18 years, the RAC has said.

According to the motoring organisation, May saw the average litre of petrol leap from 123.43p to 129.41p – a rise of almost 6p and the highest jump since the RAC began collecting fuel price data in 2000.

As a result, the cost of filling a typical 55-litre fuel tank with unleaded is now £71.18 – a £3.29 increase on the start of May.

Diesel, meanwhile, went up even more dramatically, with a 6.12p per litre increase taking the average price to 132.29p per litre. However, even this price increase was not enough to earn May the title of the worst month for diesel price rises – that dubious honour belongs to May 2008, when diesel prices shot up by 8.43p per litre.

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The news will come as little surprise to many motorists, who have watched fuel bills climb steadily. Just last week, it emerged that the average fuel price at the big four supermarkets had risen every day for eight weeks.

RAC fuel spokesman Simon Williams said the price increases were down to rising oil prices and a deterioration in the value of the pound.

‘May was a hellish month for motorists,’ he said. ‘Sadly, they have been besieged by pump price rises for three months with nearly 9p a litre being added to petrol since the beginning of March.

‘The rising oil price together with a weaker pound is a punitive combination for anyone that drives regularly. For many people there is little alternative to the car for the majority of journeys they have to make so it is therefore very difficult to avoid feeling the pinch of rising pump prices.’

However, Williams said a slight reduction in oil prices of late may improve the situation in June.

‘In the last week of May the oil price cooled a little to $76 a barrel,’ he noted. ‘That is slightly better news for motorists, as the RAC’s two-week forecast is currently showing that average prices may even reduce by a penny or so. While this isn’t much, and could easily change in response to oil trading this week, it is at least a sign that the constant rise in forecourt prices may have stopped for the time being.’