Real-world miles per gallon (all car miles ÷ all car petrol and diesel)

Average official CO2 of new cars, grams per km

What it means: the first chart is worked out on this page: the 262.4 billion miles driven by cars and taxis divided by the 26.37 billion litres of petrol and diesel they used, so it reflects real driving rather than lab tests. Since about 2020 a growing share of miles are driven on electricity, which lifts the figure, so it now overstates how far a petrol or diesel car goes on a gallon. Miles cover Great Britain and fuel the whole UK, which lowers the figure slightly. The second chart is the official test figure for new cars sold each year, including electric cars at zero; the test changed between 2018 and 2021, which explains the jump in petrol and diesel figures then. Shown for context.

Source: DfT road traffic statistics, table TRA0101; DESNZ, Energy Consumption in the UK 2026, table C8 (litres per tonne from DUKES annex A); DfT vehicle licensing statistics, table VEH0156.