The cost of fuel reached a four-year high last month and further price hikes are “inevitable”, according to the motoring group.

The average cost of unleaded is now 130.59p per litre, while diesel stands at 132.19p per litre – the highest prices seen since August 2014 and October 2014, respectively.

Back then the cost of oil was $106 a barrel compared to around $70 today.

But the weakening of the pound – from $1.70 to $1.29 – over the four-year period means it is now far more expensive for retailers to buy on the wholesale market.

The cost of filling a 55-litre family car with unleaded is £71.82 – an increase of 91p on July and £7.32 dearer than a year ago. For diesel, the equivalent cost is £73.29 for a tank today – 73p more than last month and £8.19 more expensive than at the end of August 2017.

RAC fuel spokesperson, Simon Williams, said: “August was another bad month for motorists and it’s rapidly becoming a horrible year on the UK’s forecourts and it looks like further increases are inevitable. Having benefitted from some very low prices two and a half years ago drivers get a nasty shock every time they go to fill up their cars, having to fork out more and more.

“While it’s clearly a tough time for regular motorists unfortunately there is currently no end in sight to the rising cost of fuel. With the pound at such a low against the dollar, and fuel being traded in the US currency, it will only take a moderate rise in the price of oil for some eye-wateringly high prices to be seen at the pumps.

“With many factors at play on the global oil market the price of a barrel could easily break through the $80 mark and stay there. If this were to happen it would be dire news for drivers and we could even see pump prices heading towards the record highs of April 2012 when petrol hit an average of 142p a litre and diesel 148p.”

How to bring down petrol costs

• Do your research. PetrolPrices.com lets you search for the cheapest fuel prices in your area.
• Head to supermarkets for the best deals.  “The age old myth of supermarket fuel being lower quality is not true, they all have to hit a very high standard to be sold in the UK so it will not damage the car, and they are often a few pence per litre cheaper,” says a spokesperson from PetrolPrices.com.
• Avoid motorway service stations as they can charge up to 15p per litre more.
• Try not to accelerate or brake sharply as this consumes more fuel.