UK fuel costs: budget for an August bank-holiday drive

UK drivers planning an August bank-holiday journey can estimate their fuel bill using route mileage, real-world efficiency and a verified pump price. However, the supplied Department for Energy Security and Net Zero evidence does not include the latest numerical averages, their observation date or the previous week’s figures. Quoting undated prices as current could produce a misleading budget, so no values have been invented here.

For a useful estimate:

• Include the outward and return journeys in the total mileage.
• Use the vehicle’s real-world mpg rather than its best laboratory figure.
• Insert the latest verified petrol or diesel price in pence per litre.
• Allow a modest buffer for congestion, diversions and local pump-price differences.

The weekly petrol and diesel figures must be dated

DESNZ publishes the official statistical series of weekly UK average pump prices for petrol and diesel. A reliable snapshot should show four figures: the latest petrol and diesel averages and the corresponding values from the previous week. It must also state the observation date.

Those numerical readings and dates are absent from the evidence supplied for this guide. A two-column comparison has therefore been withheld. Readers can obtain the required values from the latest DESNZ weekly road-fuel dataset before completing the calculation below.

RAC Fuel Watch provides additional consumer context about movements at the pumps. Neither source can establish which individual forecourt will be cheapest for a particular driver. A UK average combines many locations and cannot identify the lowest-priced town, region, supermarket station or motorway service area.

Calculate a journey’s fuel cost from miles and mpg

UK vehicle efficiency is commonly expressed in imperial miles per gallon, while pump fuel is sold by the litre. One imperial gallon equals 4.54609 litres.

Use this calculation:

Journey miles ÷ real-world mpg × 4.54609 × price per litre = estimated cost

If the pump price is expressed in pence per litre, divide the final result by 100 to convert pence into pounds:

(Journey miles ÷ mpg × 4.54609 × pence per litre) ÷ 100

Use total journey mileage, not just the distance to the destination. A 150-mile drive each way is a 300-mile fuel calculation before local travel or detours are added.

Representative 300-mile calculation

For a car returning 45 mpg over 300 miles:

1. 300 ÷ 45 = 6.67 imperial gallons
2. 6.67 × 4.54609 = 30.31 litres
3. Petrol estimate: 30.31 × verified petrol pence per litre ÷ 100
4. Diesel estimate: 30.31 × verified diesel pence per litre ÷ 100

This shows that the representative journey requires about 30.31 litres under the stated assumptions. A current sterling total should be published only after the dated DESNZ petrol and diesel averages have been inserted. Drivers can substitute their own mileage and real-world mpg for a more relevant estimate.

Why the amount paid may differ from the estimate

National averages are useful budgeting benchmarks, not guaranteed forecourt prices. Motorway service stations can operate under different costs and competitive conditions from nearby urban or supermarket sites. Local competition may also produce substantial variation within a short distance.

Vehicle efficiency matters just as much as the posted pump price. Heavy traffic, repeated acceleration, prolonged idling, roof boxes, extra luggage and cold starts can increase consumption. Roadworks, missed turns and holiday congestion may add miles or reduce the mpg achieved during the trip.

The estimate also assumes one consistent price. A driver who refuels at different stations could pay different rates for each part of the tank.

Safe ways to limit bank-holiday fuel spending

Check nearby pump prices before setting off, particularly before joining a motorway where alternatives may become less convenient. Compare the potential saving with the extra fuel and time required to reach another station.

Keep tyres at the vehicle manufacturer’s recommended pressure when they are cold, adjusting for load where the handbook specifies it. Incorrect pressure can affect efficiency, braking and tyre wear.

Combining errands with the main journey can avoid separate cold-start trips. Remove unnecessary heavy items, but keep all safety and emergency equipment required for the route.

Never make a sudden turn, stop in an unsafe place or follow an unfamiliar diversion merely to save a small amount on fuel. A longer detour can erase the saving, and road safety should always take priority over a cheaper advertised price.

Source: Department for Energy Security and Net Zero