Base Unit: L/100km (Liters per 100 Kilometers)

Advantages: Directly shows fuel used, additive for trip planning, easier environmental calculations

Usage: Europe, Asia, Australia, Latin America - most of the world

Lower is Better: 5 L/100km is more efficient than 10 L/100km

• liter per 100 kilometers

  Standard metric fuel consumption - widely used worldwide
• liter per 100 miles

  Metric consumption with imperial distance - transitional markets
• gallon (US) per 100 miles

  US gallon consumption format - rare but parallel to L/100km logic

Base Unit: Miles per Gallon (MPG)

Advantages: Intuitively shows 'how far you go', familiar to consumers, positive growth perception

Usage: United States, some Caribbean nations, legacy markets

Higher is Better: 50 MPG is more efficient than 25 MPG

• mile per gallon (US)

  US gallon (3.785 L) - standard American fuel economy metric
• mile per gallon (Imperial)

  Imperial gallon (4.546 L) - UK, Ireland, some Commonwealth nations
• kilometer per liter

  Metric efficiency - Japan, Latin America, South Asia

Base Unit: MPGe (Miles per Gallon Gasoline Equivalent)

Advantages: Standardized by EPA, allows direct comparison to gasoline vehicles

Usage: United States EV/hybrid rating labels, consumer comparisons

Higher is Better: 100 MPGe is more efficient than 50 MPGe

EPA Definition: 33.7 kWh of electricity = energy content of 1 gallon of gasoline

• mile per gallon gasoline equivalent (US)

  EPA standard for EV efficiency - enables ICE/EV comparison
• kilometer per kilowatt-hour

  Distance per energy unit - intuitive for EV drivers
• mile per kilowatt-hour

  US distance per energy - practical EV range metric

The Era of Cheap Gasoline:

Before the 1970s oil crisis, fuel economy was largely ignored. Large, powerful engines dominated American automotive design with no efficiency requirements.

• 1950s-1960s: Typical cars achieved 12-15 MPG with no consumer concern
• No government regulations or testing standards existed
• Manufacturers competed on power, not efficiency
• Gas was cheap ($0.25/gallon in 1960s, ~$2.40 today adjusted for inflation)

OPEC Embargo Sparks Regulatory Action:

• 1973: OPEC oil embargo quadruples fuel prices, creates shortages
• 1975: US Congress passes Energy Policy and Conservation Act (EPCA)
• 1978: Corporate Average Fuel Economy (CAFE) standards take effect
• 1979: Second oil crisis reinforces need for efficiency standards
• 1980: CAFE requires 20 MPG fleet average (up from ~13 MPG in 1975)

The oil crisis transformed fuel economy from an afterthought to a national priority, creating the modern regulatory framework that still governs vehicle efficiency worldwide.

From Simple to Sophisticated:

• 1975: First EPA testing procedures (2-cycle test: city + highway)
• 1985: Testing reveals 'MPG gap' - real-world results lower than labels
• 1996: OBD-II mandated for emissions and fuel economy monitoring
• 2008: 5-cycle testing adds aggressive driving, A/C use, cold temperatures
• 2011: New labels include fuel cost, 5-year savings, environmental impact
• 2020: Real-world data collection via connected vehicles improves accuracy

EPA testing evolved from simple lab measurements to comprehensive real-world simulations, incorporating aggressive driving, air conditioning, and cold weather impacts.

From Voluntary to Mandatory:

• 1995: EU introduces voluntary CO₂ reduction targets (140 g/km by 2008)
• 1999: Mandatory fuel consumption labeling (L/100km) required
• 2009: EU Regulation 443/2009 sets mandatory 130 g CO₂/km (≈5.6 L/100km)
• 2015: Target reduced to 95 g CO₂/km (≈4.1 L/100km) for new cars
• 2020: WLTP replaces NEDC testing for realistic consumption figures
• 2035: EU plans to ban new ICE vehicle sales (zero emissions mandate)

The EU pioneered CO₂-based standards linked directly to fuel consumption, driving aggressive efficiency improvements through regulatory pressure.

New Metrics for New Technology:

• 2010: Nissan Leaf and Chevy Volt launch mass-market EVs
• 2011: EPA introduces MPGe (miles per gallon equivalent) label
• 2012: EPA defines 33.7 kWh = 1 gallon gasoline energy equivalent
• 2017: China becomes largest EV market, uses kWh/100km standard
• 2020: EU adopts Wh/km for EV efficiency labeling
• 2023: EVs reach 14% global market share, efficiency metrics standardize

The rise of electric vehicles required entirely new efficiency metrics, bridging the gap between energy (kWh) and traditional fuel (gallons/liters) to enable consumer comparisons.

• L/100km: Already base unit (×1)
• L/100mi: L/100mi × 0.621371 = L/100km
• L/10km: L/10km × 10 = L/100km
• L/km: L/km × 100 = L/100km
• L/mi: L/mi × 62.1371 = L/100km
• mL/100km: mL/100km × 0.001 = L/100km
• mL/km: mL/km × 0.1 = L/100km

• km/L: 100 ÷ km/L = L/100km
• km/gal (US): 378.541 ÷ km/gal = L/100km
• km/gal (UK): 454.609 ÷ km/gal = L/100km
• m/L: 100,000 ÷ m/L = L/100km
• m/mL: 100 ÷ m/mL = L/100km

• MPG (US): 235.215 ÷ MPG = L/100km
• mi/L: 62.1371 ÷ mi/L = L/100km
• mi/qt (US): 58.8038 ÷ mi/qt = L/100km
• mi/pt (US): 29.4019 ÷ mi/pt = L/100km
• gal (US)/100mi: gal/100mi × 2.352145 = L/100km
• gal (US)/100km: gal/100km × 3.78541 = L/100km

• MPG (UK): 282.481 ÷ MPG = L/100km
• mi/qt (UK): 70.6202 ÷ mi/qt = L/100km
• mi/pt (UK): 35.3101 ÷ mi/pt = L/100km
• gal (UK)/100mi: gal/100mi × 2.82481 = L/100km
• gal (UK)/100km: gal/100km × 4.54609 = L/100km

Fuel Cost Calculations

Understanding fuel economy helps consumers predict operating costs accurately.

• Cost per km: (L/100km ÷ 100) × fuel price/L
• Annual Cost: (km driven/year ÷ 100) × L/100km × price/L
• Example: 15,000 km/year, 7 L/100km, $1.50/L = $1,575/year
• Comparison: 7 vs 5 L/100km saves $450/year (15,000 km at $1.50/L)

Vehicle Purchase Decisions

Fuel economy significantly impacts total cost of ownership.

• 5-Year Fuel Cost: Often exceeds vehicle price difference between models
• Resale Value: Efficient vehicles hold value better during high fuel prices
• EV Comparison: MPGe enables direct cost comparison to gasoline vehicles
• Hybrid Premium: Calculate payback period based on annual km and fuel savings

Commercial Fleet Operations

Fleet managers optimize routes, vehicle selection, and driver behavior using fuel economy data.

• Route Optimization: Plan routes minimizing total fuel consumption (L/100km × distance)
• Vehicle Selection: Choose vehicles based on mission profile (city vs highway L/100km)
• Driver Training: Eco-driving techniques can reduce L/100km by 10-15%
• Telematics: Real-time monitoring of vehicle efficiency vs. benchmarks
• Maintenance: Properly maintained vehicles achieve rated fuel economy

Cost Reduction Strategies

• 100-Vehicle Fleet: Reducing average from 10 to 9 L/100km saves $225,000/year (50,000 km/vehicle, $1.50/L)
• Aerodynamic Improvements: Trailer skirts reduce truck L/100km by 5-10%
• Idle Reduction: Eliminating 1 hour/day idling saves ~3-4 L/day per vehicle
• Tire Pressure: Proper inflation maintains optimal fuel economy

Why vehicles achieve different efficiency in different driving conditions.

City Driving (Higher L/100km, Lower MPG)

• Frequent Stops: Energy is wasted accelerating from zero repeatedly
• Idling: Engine runs at 0 MPG while stopped at lights
• Low Speeds: Engine operates less efficiently at partial load
• A/C Impact: Higher percentage of power used for climate control

City: 8-12 L/100km (20-30 MPG US) for average sedan

Highway Driving (Lower L/100km, Higher MPG)

• Steady State: Constant speed minimizes fuel waste
• Optimal Gear: Transmission in highest gear, engine at efficient RPM
• No Idling: Continuous motion maximizes fuel use efficiency
• Speed Matters: Best economy typically 50-65 mph (80-105 km/h)

Highway: 5-7 L/100km (34-47 MPG US) for average sedan

How hybrids achieve superior fuel economy through regenerative braking and electric assist.

• Regenerative Braking: Captures kinetic energy normally lost as heat, stores in battery
• Electric Launch: Electric motor handles inefficient low-speed acceleration
• Engine Off Coasting: Engine shuts off when not needed, battery powers accessories
• Atkinson Cycle Engine: Optimized for efficiency over power
• CVT Transmission: Keeps engine in optimal efficiency range continuously

Hybrids excel in city driving (often 4-5 L/100km vs 10+ for conventional), highway advantage is smaller

Historical reasons. The US developed MPG (efficiency-based: distance per fuel) which sounds better with higher numbers. Europe adopted L/100km (consumption-based: fuel per distance) which aligns better with how fuel is actually consumed and makes environmental calculations easier.

Use the inverse formula: L/100km = 235.215 ÷ MPG (US) or 282.481 ÷ MPG (UK). For example, 30 MPG (US) = 7.84 L/100km. Note that higher MPG equals lower L/100km - better efficiency both ways.

UK (Imperial) gallon = 4.546 liters, US gallon = 3.785 liters (20% smaller). So 30 MPG (UK) = 25 MPG (US) for the same vehicle. Always verify which gallon is used when comparing fuel economy.

MPGe (Miles Per Gallon equivalent) compares EV efficiency to gas cars using the EPA standard: 33.7 kWh = 1 gallon of gasoline equivalent. For example, a Tesla using 25 kWh/100 miles = 135 MPGe.

EPA tests use controlled lab conditions. Real-world factors reduce efficiency by 10-30%: aggressive driving, AC/heating use, cold weather, short trips, stop-and-go traffic, underinflated tires, and vehicle age/maintenance.

L/100km is easier: Cost = (Distance ÷ 100) × L/100km × Price/L. With MPG, you need: Cost = (Distance ÷ MPG) × Price/gallon. Both work, but consumption-based units require fewer mental inversions.

Regenerative braking captures energy during stops, and electric motors assist at low speeds where gas engines are inefficient. Highway driving uses mostly the gas engine at constant speed, reducing the hybrid advantage.

Use MPGe for direct comparison. Or convert: 1 kWh/100km ≈ 0.377 L/100km equivalent. But remember EVs are 3-4x more efficient at the wheel - most 'loss' in comparison is due to different energy sources.