UK fuel prices: Work out the cost of an October journey

The price on the pump is the number that determines what a UK driver pays for an October journey. The government’s weekly petrol and diesel averages offer a useful benchmark, but a local forecourt may charge more or less. Before setting off, check the latest dated average, then use the price displayed where you plan to fill up to estimate your own cost.

Use the dated UK average as a benchmark

The Department for Energy Security and Net Zero publishes weekly UK average retail prices for petrol and diesel. Each release identifies a reporting week. Read that date alongside the figures: an average from an earlier week is context for today’s pump price, not a quote you can expect at a particular station.

To make a useful comparison, look at the latest dated release and note the petrol and diesel averages in pence per litre. Then compare the relevant average with the price displayed at the forecourt you intend to use. This article does not quote a current weekly figure because the reporting week and its prices need to be read together.

A UK average combines prices from many places. It does not establish the cheapest station on your route or predict what a motorway service area, supermarket or neighbourhood forecourt will charge. It also says nothing about how much fuel your particular car will use in traffic, on hills or at motorway speeds.

A 180-mile petrol journey: one worked example

Suppose your route is 180 miles, your car returns 45 miles per imperial gallon, and your chosen forecourt displays 145.9p per litre for petrol. The pump price is an illustrative assumption for this calculation, not a current price claim.

First, divide the distance by fuel economy: 180 ÷ 45 = 4 imperial gallons. One imperial gallon is approximately 4.546 litres, so the journey would use about 18.18 litres. Convert the displayed price to pounds, £1.459 per litre, and multiply: 18.18 × £1.459 = about £26.53.

The same method works for diesel: use your diesel vehicle’s consumption and the diesel price shown at the forecourt. Do not assume that the difference between the national petrol and diesel averages is the difference between two vehicles’ journey costs. Their fuel consumption may differ substantially.

If your dashboard or vehicle handbook gives consumption in litres per 100 kilometres, multiply the journey distance in kilometres by that figure and divide by 100. That gives estimated litres used; multiply those litres by the forecourt price per litre.

Why your final bill may differ

The calculation estimates fuel used over the journey. Your actual spend at the pump also depends on how much fuel is already in the tank and whether you fill it beyond what the trip requires. A return journey needs the return distance included unless the 180 miles already covers both directions.

Treat the vehicle’s consumption figure as a planning estimate. Passengers, luggage, weather, congestion and driving speed can change real-world fuel use. If you know your car’s recent average from similar journeys, it may give you a more useful estimate than a published vehicle figure.

For the most relevant October estimate, check the reporting week on the government’s weekly fuel-price page, then check the actual petrol or diesel price at your intended stop. Recalculate if either your route or that forecourt price changes.

Source: UK Department for Energy Security and Net Zero