Common fuel efficiency conversions

MPG (US)	MPG (UK)	km/L	L/100km
20	24.0	8.50	11.76
25	30.0	10.63	9.41
30	36.0	12.75	7.84
35	42.1	14.88	6.72
40	48.1	17.00	5.88

US vs UK gallons

A US gallon is 3.785 L while a UK (imperial) gallon is 4.546 L. This means UK MPG figures are about 20% higher than US MPG for the same vehicle. Always check which system is being used when comparing fuel economy ratings.

L/100km: an inverse measure

Unlike MPG and km/L where higher numbers indicate better efficiency, L/100km is a consumption measure; lower numbers mean the vehicle uses less fuel per distance traveled. The formula is: L/100km = 100 ÷ km/L. This inverse relationship often confuses drivers switching between unit systems - a drop from 10 to 8 L/100km is an improvement, while a rise from 30 to 40 MPG is also an improvement. Both describe the same change.

Real-world benchmarks

Vehicle type	MPG (US)	L/100km	Example
Economy car	35–40	5.9–6.7	Toyota Corolla
SUV	23–28	8.4–10.2	Honda CR-V
Hybrid	50–58	4.1–4.7	Toyota Prius
Pickup truck	17–22	10.7–13.8	Ford F-150 (gas)
Luxury SUV	18–24	9.8–13.1	BMW X5

EPA label reading guide

US EPA fuel economy labels show three ratings: city (stop-and-go traffic), highway (steady-speed driving), and combined (the weighted average). The combined rating reflects 55% city and 45% highway driving, representing an average US driver's mix. Real-world fuel economy often differs from EPA estimates due to driving style, terrain, temperature, and load.