What this tool does
This tool converts fuel economy measurements from miles per gallon using the US gallon to other common fuel efficiency units. The US gallon equals 3.785 liters, making it approximately 17% smaller than the UK Imperial gallon. This difference means that fuel economy figures are not directly comparable between US and UK systems without conversion. This converter handles both linear conversions (to km/L, miles/L, and MPG UK) and the inverse relationship with consumption-based units like liters per 100 kilometers. All conversions are bidirectional and support any combination of the available units.
How it calculates
The tool uses the US gallon (3.78541 liters) as the reference. Direct conversion factors from 1 MPG (US): 1.20095 MPG (UK), 0.425144 km/L, and 0.264172 miles/L. For liters per 100 km, the conversion is inversely proportional: L/100km = 235.215 / MPG (US). The tool converts any input to MPG (US) as an intermediate step, then converts from MPG (US) to the target unit, ensuring accuracy for all unit combinations.
Who should use this
- **US car buyers** comparing domestic and imported vehicle efficiency ratings - **International travelers** understanding fuel economy in foreign rental cars - **Auto enthusiasts** comparing performance specifications across markets - **Environmental analysts** standardizing emissions data from different countries
Worked examples
Example 1: A US car rated at 32 MPG converts to UK MPG: 32 x 1.20095 = 38.43 MPG (UK). Example 2: Converting 32 MPG (US) to L/100km: 235.215 / 32 = 7.35 L/100km. Example 3: A European car rated at 4.8 L/100km converts to US MPG: 235.215 / 4.8 = 49.00 MPG (US). Example 4: A midsize sedan at 30 mpg (US) converts to 12.75 km/L (30 x 0.425144) and 7.93 miles per liter (30 / 3.78541).
Limitations
This tool provides mathematically exact conversions but does not account for differences between fuel economy test procedures across countries. The EPA (US), WLTP (Europe), and JC08 (Japan) test cycles produce different results for the same vehicle. Real-world fuel economy varies based on driving conditions, vehicle maintenance, and fuel quality. The tool does not handle electric vehicle efficiency metrics like MPGe or kWh/100 miles.
FAQs
Q: Why is the UK MPG number always higher than US MPG? A: Because the UK Imperial gallon is larger (4.546 L vs 3.785 L). A larger gallon means more fuel per unit, so a vehicle travels more miles per gallon in the UK system, resulting in a higher number for the same actual efficiency. The ratio is about 1.201.
Q: What is the most universal fuel economy unit? A: Liters per 100 kilometers (L/100km) is used by most countries worldwide. It is a consumption-based metric where lower values indicate better efficiency. Many analysts prefer it because fuel savings scale linearly with the metric.
Q: How accurate are EPA MPG ratings? A: EPA ratings are estimates based on standardized test cycles. Real-world fuel economy typically falls 10-20% below EPA estimates, depending on driving habits, terrain, and conditions.
Q: Can I use this for diesel vehicles too? A: Yes, the unit conversions are identical for gasoline and diesel vehicles. The conversions relate to volume of fuel consumed per distance, regardless of fuel type.
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