The findings are part of a massive survey that has uncovered the cheapest and most expensive parts of the UK where fleets buy fuel.
Fleet drivers filling up in central Scotland – around Glasgow and Edinburgh – win what is described as the 'fuel price lottery', while those topping up the tank in East Anglia lose out.
The survey was carried out by Castle Fuel Cards and found that the average price of unleaded petrol in central Scotland last week was 77.4 pence per litre, whereas in East Anglia it was 78.6 pence per litre.
Scotland outside the central region – into the Highlands and other rural areas – is the most expensive area in the UK as a whole, with petrol averaging 78.9 pence per litre.
Castle Fuel Cards found that prices also tended to be above the national average in south west England, Wales, the south east and the west Midlands.
It suggests that a 200-car fleet operating in the Midlands could cut its typical annual fuel bill of about £330,000 by nearly £14,000, or 4.2%, if it encouraged drivers towards the lowest-priced outlets such as supermarkets, rather than buying fuel at the average regional price.
'Fleets are playing a postcode lottery whenever their drivers stop to refuel,' said Teresa Maynard, head of fuel at Castle Fuel Cards. 'Even so, they can play the game to their advantage by making sure their drivers always aim to buy below the average price.'
The Castle Fuel Card survey highlights considerable price variations within regions.
In the east Midlands, the difference between the most and least expensive petrol is equivalent to about £3.40 for a fill-up but in north west England, the variance is more than £7 and in the north of Scotland it is nearly £7.60.