The data revealed that a litre of unleaded rose by 0.33p on the price at the start of August to hit 111.5p at the end.
This was mirrored by an increase in the cost of diesel, which rose by 0.77p to reach 112.81p – close to one of the highest prices recorded in 2016.
The RAC said that although the price rises are only slight, they have had the effect of cancelling out the lower costs that motorists were enjoying in July.
At the start of August, supermarkets up and down the country appeared to heed calls from the RAC for a drop in fuel prices by taking 2p off the price of a litre of both petrol and diesel.
While this brought lower average prices in the first week of the month, drivers were paying nearly 2p more from the end of the second week of the month.
To fill a family car with a 55-litre tank, motorists are now having to spend £61.33 for unleaded and £62.05 for diesel.
There were also some regional variations in the fuel price rises, with the north of England seeing the larger average increase to bills in August, with a litre of petrol up 0.57p to 111.18p.
In Yorkshire and Humber, meanwhile, diesel prices saw their sharpest increase, coming in at 112.35p, up by 0.97p.
However, the figures showed that the South East remained the most expensive region for fuel, with a litre of unleaded on average selling for 111.93p and diesel at 113.22p.
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RAC fuel spokesman Simon Williams said that despite the increases, drivers were able to enjoy some savings in July, which will have helped those who took children away during the summer holidays.
He added: “It is still the case however that the average price of unleaded petrol grew at its slowest rate in more than a year in August, and we are thankfully still a little way off the sorts of average prices we saw earlier in 2015 when petrol hit 117p per litre and diesel nearly 121p per litre.”
It is thought the rising prices can be attributed to the higher cost of a physical barrel of oil, which increased by $6 in August to hit around $46.28.
Simon Williams added that a planned meeting between oil producers in September could help to provide a clearer picture of fuel price trends for the rest of the year.