The Good Green Cars Glossary

An ongoing and occasionally updated list of green car terms and acronyms.

B20, B100: Seen at diesel pumps, these designations indicate the amount of biodiesel blended with petroleum-based diesel. So B20 is 20% biodiesel, 80% low-sulfur diesel, while B100 is 100% biodiesel.

Biodiesel: Diesel fuel made at least partly from non-petroleum sources, such as used restaurant grease. Most diesel-powered vehicles can use biodiesel without conversion or alteration of the engine.

Bioethanol: A vehicle fuel based on starchy plant materials, commonly corn in the U.S. It has a lower emissions rating than petroleum. Also known as ethanol.

CAFE Standards: Corporate Average Fuel Economy. Each automaker must average the mileage of every vehicle it builds. The standards were enacted in 1975 to increase overall fuel efficiency. The standard for 2009 is 27.5 mpg for cars, 20.7 mpg for light trucks, and 23.1 mpg for trucks under 8500 pounds.

Diesel: A petroleum-based fuel that gets higher fuel efficiency than gasoline. It tends to have more tailpipe emissions, but technological innovations in the past decade have nearly erased this concern and dropped diesel emissions to near gasoline levels.

E85: A fuel blend that contains 85% ethanol, 15% gasoline.

EPA: Environmental Protection Agency. Together with the Department of Energy, the EPA issues mileage and emissions ratings for all cars sold in the U.S. See

Extended Range Electric Vehicle: A type of PHEV where the car drives entirely on electric power, but there is a small gasoline engine on board that runs a generator to provide electricity for the batteries and electric motor. The addition of the gasoline engine allows the electric motor to go further on a charge.

Ethanol: A high-octane, low-emissions fuel long used in racing. Now it’s made from renewable plant materials and can be used in regular vehicles, though it gets lower fuel economy ratings than gasoline.

EV: Electric Vehicle. These cars have only batteries and an electric motor–no gasoline or other fuel required, and no emissions are released into the air. They are refueled by plugging the batteries into an outlet.

Flex Fuel: A vehicle that can accept regular gasoline or an ethanol blend, such as E85.

Fuel Efficiency: Using the least amount of fuel to drive the farthest number of miles. This can be measured miles per gallon, which is standard in the U.S., or in gallons per mile, which is more common in the rest of the world.

Hybrid: In the automotive sense, this is a vehicle that has a gasoline-powered engine and an electric engine that work together to deliver better gas mileage, usually 40+ mpg. The batteries are recharged by systems like regenerative braking. The 1999 Honda Insight was the first commercially available hybrid; the Toyota Prius became the first popular hybrid car.

Hydrogen Fuel Cell: These cells use hydrogen gas and air to create an electrical current to power a vehicle, with only water as a byproduct. Creating an infrastructure of hydrogen fueling stations has been an obstacle to the manufacture of hydrogen-powered cars.

ICE: Internal Combustion Engine. The same old gasoline-powered engine we’ve been driving all our lives.

Liquified Natural Gas: Natural gas that has been cooled to form a transportable liquid. Vehicles that run on LNG cannot use any other type of fuel with major modifications.

Lithium Ion: A type of battery used in cell phones, laptops, and electric cars. These batteries store a lot of energy for their weight.

LNG: Liquified Natural Gas.

MPG: Miles per gallon. The number of miles a car can travel on one gallon of gasoline or other liquid fuel.

NHTSA: National Highway Traffic Safety Administration. The NHTSA administrates the CAFE Standards, based on fuel efficiency data from the EPA.

NiCd: Nickel Cadmium, sometimes called NiCad. A type of rechargeable battery used in electric cars.

NiMH: Nickel Metal Hydride. A type of rechargeable battery used in electric cars.

PHEV: Plug-in Hybrid Electric Vehicle. See Plug-in Hybrid.

Plug-in Hybrid: A vehicle that has a gasoline-powered engine and a bank of batteries that can be recharged by plugging them into an outlet. These vehicles usually use the electric motor for 40 or so miles, then the gasoline engine as a backup. The supposedly forthcoming Chevy Volt is a PHEV.

Vehicle to Grid: Technology that allows electric utility companies to reclaim small amounts of energy from plugged-in EVs. Boulder, Colorado, has a pioneering VtG program.

Water Car: Proponents of the idea of running a car on water say it’s a similar energy conversion process to hydrogen fuel cells. The conversion of energy, though, seems to lose a lot along the way, making any benefit null.

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  1. Patrick’s avatar

    Great list: I would add EREV.

    Extended Range Electric Vehicle – A type of PHEV where all the propulsion is provided by the electric motor. The gasoline engine is only used to run a generator for provide electricity for the batteries and electric motor.

  2. kristen’s avatar

    Great addition! I’ve put it in the glossary, with a wee bit of editing. Thanks for the suggestion.

    If anyone else would like to see a term added, please leave a comment on this post. I’d love to see this list be as complete as possible, and as helpful as I can make it for folks new to alternative fuels.

    Kristen Hall-Geisler

  3. Nils Anderson’s avatar

    You might redefine Diesel as a fuel that contains 18 percent more energy per gallon becauses it weighs 18 percent more and it’s price is usually 18 percent more than gasoline but that coupled with it’s twice costly engine should give 20 percent greater mileage.

    Nils Anderson
    Mechanical Engineer
    Scottsdale, AZ