Diesel prices recorded their biggest monthly fall since records began in 2000 during June, while petrol prices also posted one of their largest monthly declines on record, according to RAC Fuel Watch data. The average price of diesel fell by 16.6p a litre during the month, dropping from 183.75p at the beginning of June to 167.14p by 30th June. The RAC said this surpassed the previous record monthly fall of 11.92p, recorded in May 2023.