US vs UK Gallon MPG
The imperial (UK) gallon is about 4.55 liters versus the US gallon’s 3.79 liters — roughly 20% larger. So a car that returns 40 MPG in the US shows about 48 MPG in the UK, even though nothing about the car changed.
Use the converter to move cleanly between US MPG, UK MPG, L/100km, and km/L.