⛽ Fuel Efficiency Converter

Quick Reference Table

Vehicle Fuel Efficiency Ranges

Understanding Fuel Efficiency Units

Miles Per Gallon - US (MPG)

Definition: The number of miles a vehicle can travel on one US gallon of fuel. The US gallon equals 3.785 liters. Higher MPG means better fuel efficiency.

History: Became standard in United States during early automotive era (1900s). EPA established standardized testing in 1970s. "City" and "Highway" MPG ratings introduced to reflect different driving conditions.

Current Use: Primary fuel economy measurement in United States. Required on all new vehicle window stickers (Monroney sticker). EPA ratings guide consumer purchases. Average new car (2024): ~27 MPG combined. CAFE standards mandate minimum fleet averages. Used in automotive reviews and comparisons throughout North America.

Miles Per Gallon - Imperial/UK (MPG)

Definition: Miles traveled per Imperial gallon. The Imperial gallon equals 4.546 liters, about 20% larger than US gallon. UK MPG numbers are therefore higher than US MPG for the same vehicle.

History: Traditional British measurement predating metrication. UK began transition to metric in 1970s but MPG persisted in automotive context due to cultural familiarity.

Current Use: Still used in United Kingdom and some Commonwealth countries alongside L/100km. UK fuel sold in liters but efficiency often discussed in MPG. Conversion: UK MPG = US MPG × 1.201. Being gradually replaced by metric measurements but remains popular in consumer discussions.

Liters Per 100 Kilometers (L/100km)

Definition: The volume of fuel (in liters) consumed to travel 100 kilometers. Lower numbers indicate better efficiency. The international metric standard for fuel consumption.

History: Adopted with metrication in Europe, Canada, Australia, and most of the world during 1970s-1990s. Represents fuel consumption rather than distance per fuel (inverse relationship to MPG).

Current Use: Standard measurement in Europe, Canada, Australia, Asia, South America, and most countries worldwide. Official government fuel economy ratings. Vehicle specifications list L/100km. Easier for mental math with metric fuel prices. Typical modern car: 6-8 L/100km. More intuitive for fuel consumption calculations (multiply by trip distance in 100km units).

Kilometers Per Liter (km/L)

Definition: The number of kilometers traveled per liter of fuel consumed. Similar concept to MPG but using metric units. Higher numbers mean better efficiency.

History: Natural metric equivalent to MPG. Less common than L/100km but still used in some regions.

Current Use: Common in Japan, India, parts of Asia, and Latin America. Some countries use both km/L and L/100km. Vehicle specifications may list both. Easier to understand for people familiar with MPG concept. Conversion from L/100km: km/L = 100 ÷ L/100km. Typical car: 12-17 km/L.

Miles Per Liter (MPL)

Definition: Miles traveled per liter of fuel. Hybrid unit combining imperial distance with metric fuel volume. Less common than other measurements.

History: Emerged during transition periods when countries adopted metric fuel sales but retained mile-based road systems.

Current Use: Occasionally used in UK and countries mixing imperial/metric systems. Not a standard rating but appears in some fuel economy discussions. Useful for quick mental calculations when buying fuel in liters but thinking in miles.

Frequently Asked Questions

How do I convert MPG to L/100km?

Formula: L/100km = 235.214 ÷ MPG (US) or 282.481 ÷ MPG (UK). Example: 30 MPG (US) = 235.214 ÷ 30 = 7.84 L/100km. This is inverse - higher MPG means lower L/100km. Quick estimate: divide 235 by MPG for approximate L/100km. To convert L/100km to MPG: MPG = 235.214 ÷ L/100km.

What's the difference between US and UK MPG?

The gallon size. US gallon = 3.785 liters. Imperial (UK) gallon = 4.546 liters (20% larger). Same vehicle gets ~20% higher MPG rating in UK system. Conversion: UK MPG = US MPG × 1.201. Example: 30 MPG (US) = 36 MPG (UK). Always specify which gallon when comparing fuel economy internationally.

What's good fuel economy for a car?

Depends on vehicle type and region. US standards: Excellent >40 MPG (5.9 L/100km), Good 30-40 MPG (5.9-7.8 L/100km), Average 25-30 MPG (7.8-9.4 L/100km), Poor <20 MPG (>11.8 L/100km). Hybrids achieve 40-60 MPG. Electric vehicles use MPGe (equivalent). Small efficient cars: 35-45 MPG. Large SUVs: 18-25 MPG.

Why do real-world MPG differ from EPA ratings?

EPA tests on dynamometers under controlled conditions. Real-world factors: aggressive driving reduces MPG 15-30%, cold weather decreases efficiency 10-30%, AC use reduces MPG 10-20%, roof cargo/racks reduce MPG 2-8%, tire pressure affects efficiency, traffic conditions vary greatly. EPA now includes city/highway/combined ratings. Highway driving typically 20-30% more efficient than city. Actual MPG often 10-20% lower than EPA estimates.

How do I improve my fuel economy?

Key strategies: maintain steady speeds (avoid rapid acceleration/braking), keep tires properly inflated (can improve 3%), remove excess weight (100 lbs reduces MPG 1%), use cruise control on highways, avoid excessive idling, combine errands into single trips, maintain vehicle (clean air filters, regular oil changes), drive smoothly (anticipate traffic), close windows at highway speeds, avoid roof cargo when possible. Driving 55 vs 75 mph improves fuel economy 25%.

What is MPGe for electric vehicles?

Miles Per Gallon equivalent (MPGe) measures electric vehicle efficiency. EPA defines 33.7 kWh of electricity as equivalent to one gallon of gasoline in energy content. Example: Tesla Model 3 rated 132 MPGe means it travels 132 miles using 33.7 kWh (energy equivalent of 1 gallon). Allows comparison between gas, hybrid, and electric vehicles. Most EVs achieve 100-140 MPGe.

How much fuel does idling waste?

Idling uses 0.2-0.5 gallons per hour depending on engine size. Modern engines use more fuel restarting than idling for less than 10 seconds. Rule: if stopped >10 seconds, turn off engine to save fuel. Hour of idling = 5-10 miles of driving wasted. Remote start for comfort wastes fuel. Block heaters in cold climates more efficient than long warm-ups.

Does cruise control save gas?

Yes, on flat highways. Maintains constant speed better than humans, preventing micro-accelerations that waste fuel. Saves 7-14% on highways. BUT: disable on hills - cruise maintains speed uphill by consuming more fuel. Better to manually control speed on hilly terrain. Most effective on long, flat highway drives. Not beneficial in city traffic with frequent stops.

Common Uses for Fuel Efficiency Conversion

• Car Shopping: Comparing vehicles with different measurement systems
• International Relocation: Understanding fuel economy in new country
• Trip Planning: Estimating fuel costs for road trips
• Vehicle Imports: Converting specifications from other markets
• Fleet Management: Standardizing efficiency metrics
• Environmental Impact: Calculating carbon emissions from fuel use
• Budget Planning: Estimating monthly fuel expenses
• Automotive Reviews: Understanding international vehicle tests

Fuel Efficiency Conversion Tips

1. Remember the inverse: Higher MPG = Lower L/100km (opposite directions)
2. Quick MPG to L/100km: Divide 235 by MPG for rough estimate
3. US vs UK MPG: Multiply US by 1.2 to get UK (or divide by 0.833)
4. km/L to L/100km: Divide 100 by km/L value
5. Compare apples to apples: Always verify which measurement system
6. Real-world expectations: Subtract 10-20% from official ratings
7. Savings calculation: L/100km more accurate for fuel cost estimates

Interesting Fuel Efficiency Facts

• Most efficient production car: 100+ MPG (hybrid/PHEV models)
• 1980s average: 20 MPG; 2024 average: 27 MPG (35% improvement)
• Worst fuel economy ever: M1 Abrams tank: 0.6 MPG (392 L/100km)
• Formula 1 car: ~3-5 MPG during race (extreme performance)
• Motorcycle efficiency: 40-70 MPG typical (better than most cars)
• Semi-trucks: 6-8 MPG loaded (29-39 L/100km)
• Cruise ships: measured in gallons per mile, not MPG
• 747 airplane: ~0.2 MPG overall, but 100 MPG per passenger
• Hypermiling record: >100 MPG in standard Prius through technique
• Diesel advantage: 20-40% better fuel economy than equivalent gas engine
• Weight impact: every 100 lbs reduces fuel economy by ~1-2%
• Aerodynamics: reducing drag by 10% improves highway MPG ~5%

Fuel Economy by Country Standards

United States

Uses MPG (US gallons). EPA testing provides City/Highway/Combined ratings. CAFE (Corporate Average Fuel Economy) standards require fleet average ~40 MPG by 2026. Window stickers mandatory on new vehicles. Gas guzzler tax on vehicles under 22.5 MPG combined.

Europe

Uses L/100km officially. WLTP (Worldwide Harmonized Light Vehicles Test Procedure) replaced NEDC in 2017. Target: fleet average 95 g CO₂/km (~61 MPG / 3.8 L/100km) by 2021. Strict emissions standards drive efficiency improvements. Diesel common (better fuel economy).

Canada

Uses both L/100km (official) and MPG in consumer discussions. Similar standards to US due to integrated auto market. EnerGuide label shows L/100km ratings. Fuel sold in liters; distances in kilometers.

Asia

Japan uses km/L (JC08 or WLTC test). India uses km/L. China uses L/100km. Regulations vary by country. Small, efficient vehicles dominate due to fuel costs and urban density.

Calculating Fuel Costs

Using MPG (US)

Cost = (Distance in miles ÷ MPG) × Price per gallon. Example: 300 miles ÷ 25 MPG = 12 gallons × $3.50 = $42.00

Using L/100km

Cost = (Distance in km ÷ 100) × L/100km × Price per liter. Example: 500 km ÷ 100 = 5 × 8 L/100km = 40 liters × $1.50 = $60.00

Comparing Fuel Economy

Calculate annual fuel cost difference. Vehicle A: 25 MPG, Vehicle B: 35 MPG. Driving 12,000 miles/year at $3.50/gallon. A uses 480 gallons ($1,680). B uses 343 gallons ($1,200). Savings: $480/year with more efficient vehicle.