Glossary
Carbon Footprint (Fuel)
Direct Answer / TL;DR
What is Carbon Footprint (Fuel)?
The total greenhouse gas emissions produced by burning a litre or gallon of petrol or diesel — typically expressed in grams of CO2 per kilometre (g/km) or kg of CO2 per litre. Petrol produces approximately 2.31 kg CO2 per litre; diesel approximately 2.68 kg CO2 per litre.
Why does it matter for UK drivers?
When petrol burns in an engine, each carbon atom in the hydrocarbon fuel combines with two oxygen atoms to produce CO2. A litre of unleaded petrol contains approximately 630g of carbon, producing approximately 2.31 kg of CO2 when fully combusted. Diesel is denser in hydrocarbons — approximately 2.68 kg CO2 per litre.
For a car doing 40 MPG (consuming 0.125 litres per mile), each mile produces approximately 290g of CO2. Over a year at 10,000 miles, that's 2.9 tonnes of CO2 — broadly equivalent to the annual carbon footprint of one economy long-haul flight.
Ethanol (in E10 fuel) is partially carbon-neutral on a lifecycle basis — the CO2 released when it burns was absorbed by the crop during growth. This is why E10 reduces lifecycle carbon intensity by approximately 2% compared to E5, even though the combustion CO2 figure is similar.
The DVLA VES API returns the CO2 g/km figure for each registered vehicle. WorthThePump uses this figure as a secondary input for MPG estimation (via the CO2 formula fallback): MPG = 6,272.2 ÷ CO2 (g/km) for petrol; ÷ 1.178 for diesel. This formula is derived from the relationship between combustion chemistry and fuel energy density.
For drivers who want to reduce their carbon footprint, the most impactful change is reducing miles driven — not switching fuel stations. But choosing to fill up near your existing route rather than making a dedicated trip does reduce dead mileage emissions.
Related terms
Further reading
Now you know what Carbon Footprint (Fuel) means —
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