The price of filling up at the pumps costs £2 less than it did last month, figures have shown.
RAC Fuel Watch has said petrol has fallen by more than 4p a litre to £1.12 as the price of oil plummeted to a six-year low.
The watchdog said 5p had been shaved off the price of diesel, taking the average cost down to £1.10.
Carmarthenshire bus company boss Tom Thomas welcomed the news, saying he was saving £2,890 a month in fuel.
"In March 2014, we bought 8,500 litres and it cost us around £10,370," the director of Brodyr Williams Bus Company in Upper Tumble said.
"In July this year we bought the same amount and we paid £7,480 - it makes a big difference.
"It does help us as a company because things were very tough when prices were high... some of the largest buses we have do seven or eight miles to the gallon."
The fall in pump prices has been driven by a dramatic reduction in the price of oil.
In the run-up to August, oil was at a consistent $60 (£40) a barrel, but dipped below $50 (£33) a barrel at the start of the month and stayed below $50 for the whole month, reaching a low point of $41.87 (£27) on 24 August.
RAC fuel spokesman Simon Williams said: "We thought July had been a good month for motorists but August proved to be better still due to world oil prices reaching their lowest since February 2009."