- Originated by
- US Environmental Protection Agency (EPA), under the Energy Policy and Conservation Act of 1975.
- First formalized
- 1975 — Corporate Average Fuel Economy (CAFE) standards signed into US law after the 1973 OPEC oil crisis.
- Origin
- Washington, D.C., USA; parallel Japanese (10-mode) and European (NEDC) cycles followed.
How it came to be
The 1973 OPEC oil embargo quadrupled US gas prices in months and shocked Congress into action. The Energy Policy and Conservation Act of 1975 created CAFE, demanding manufacturers double their average fuel economy by 1985. EPA window-sticker MPG ratings became mandatory at the same time. Europe followed with the New European Driving Cycle (NEDC) in 1992, replaced by the more realistic WLTP in 2017. The MPGe metric — letting EVs and gas cars be compared on the same window sticker — debuted in 2010 for the Chevrolet Volt and Nissan Leaf.
Key milestones
- 1973OPEC oil embargo quadruples US fuel prices.
- 1975US Congress passes CAFE; EPA window-sticker MPG launched.
- 1992Europe adopts NEDC test cycle.
- 2008EPA revises window-sticker formulas to better match real-world driving.
- 2010MPGe debuts on the Chevy Volt and Nissan Leaf.
- 2017Europe replaces NEDC with WLTP, raising apparent consumption ~20%.
- 2023EU agrees to ban new ICE car sales from 2035.
MPG vs MPGe
MPG measures miles driven per gallon of gasoline. MPGe (miles per gallon equivalent) converts electricity to its energy equivalent in gasoline (33.7 kWh = 1 gallon). A 110 MPGe EV uses roughly one-third the energy of a 36 mpg gas car for the same distance.
EPA city, highway, combined
City is stop-and-go testing; highway is steady cruising; combined weights them 55/45. Hybrids excel in city (regen braking, engine-off at lights). Pure-gas cars usually do best on highway. EVs are the opposite of gas — city is more efficient than highway because of regen.
Why your MPG never matches the sticker
EPA tests use a controlled dyno cycle with mild acceleration. Real-world driving adds AC use, cold weather (10–30% range loss in EVs), wind resistance over 70 mph, hills, and aggressive driving. Most owners see 10–20% below the EPA combined number.
What actually saves fuel
Slowing down (75→65 mph saves ~15% on most cars), proper tire pressure (5 psi low = ~2% worse mpg), removing roof boxes (drag), accelerating gently, and combining trips to keep the engine warm. Driving habits affect economy 20–30% — more than any car-shopping decision.
Premium vs regular fuel
Cars that require premium (Audi, BMW, Porsche, AMG, most turbo engines) will lose power and risk damage on regular. Cars that recommend premium will run on regular with slightly less power and economy — usually a wash on cost. Cars designed for regular gain nothing from premium.