The Greener Driving Jargon Buster

Toyota's electric car

Get to know all the vital terms associated with green car technology in our jargon-buster lowdown.

With declining oil production, rising petrol prices, worsening worldwide energy shortages and increasing environmental pressures, the environmental performance of cars is at long last becoming more of a big issue for manufacturers and the public.

When buying a car these days you’ll need to know your carbon-offsetting to your hydrocarbons so to help you along your way, find out the terms that will become common parlance in the years to come.

The Jargon Buster

Biofuels – fuels such as bioethanol or biodiesel are produced from renewable sources, such as crops. They can be used 'neat', or blended with crude-oil fuels; E85, for example, is 85% bioethanol mixed with 15% regular unleaded.

Carbon Dioxide (CO2) – A greenhouse gas, CO2 is said to cause global warming. It is a direct measure of fuel efficiency – using less fuel produces less CO2. It is measured in ‘grams per kilometre’; cars emitting 130g/km or less are generally considered ‘low-CO2’ models.

Carbon Monoxide (CO) – Caused by incomplete combustion, engine efficiency can partly be measured by CO emissions. The gas is poisonous, odourless and colourless.

Carbon-Offsetting – Paying an organisation a set amount according to estimates of how much CO2 you produce. This money is then invested in CO2 reduction schemes, to ‘offset’ that amount of CO2.

Company Car Tax – Under ‘Benefit in Kind’ rules, the government taxes company car drivers based on how much the car costs to buy and how much CO2 it produces. Drivers of cars emitting less CO2 pay less tax.

Euro IV/ Euro V Emissions Standards – The industry-standard exhaust-gas regulations, which all new cars have to meet (Euro V kicks in from 2009). These standards have steadily tightened since 1993, and define the limits of exhaust pollutants cars can legally produce.

Fuel Economy (mpg) – A measure of how much fuel a car uses when driving around. Each car has different economy, measured in ‘miles per galon’ – how many miles it can travel to each gallon of fuel.

Hybrid – A car which is powered by a combination of sources, such as petrol and electricity. Diesel-electric hybrids are also on the way.

Hydrocarbons (HC) – These exhaust gases are said by some to be cardinogenic and cause low-level ozone when mixed with other exhaust pollutants.

Hydrogen – A highly flammable gas, hydrogen produces only water when burnt. Carmakers plan to use it its liquid state, and see it as key to the development of the zero-emission electric fuel cell.

Litres/ 100km – The European measure of fuel economy. It states an exact quantity of fuel needed to cover a set distance so, unlike miles per gallon, a lower figure is better.

LPG/ CNG – Liquefied petroleum gas is a more refined by-product of crude oil production, producing less CO2. It can be found at many filling stations. Compressed natural gas is like cooking gas, but rarely found in the UK as a vehicle fuel.

Nitrogen Oxides (NOx) – Smog-forming pollutants associated with breathing disorders, they can mix with hydrocarbons to form low-level ozone. Caused by high engine combustion temperatures, they are a particular issue with diesels: future Euro VI emissions standards are already targeting them, which may lead to the introduction of NOx filters.

Particulates – The ‘black smoke’ of some diesels, particulate emissions aggravate breathing disorders and are an issue in urban areas. Very fine ‘PM10s’ are said to be particularly harmful.

Particulate Filter – Fitted to some diesel cars, this traps and removes particulates from the exhaust gasses. In Which? tests, cars fitted with them emit virtually no harmful particulates.

Plug-In Hybrid – A petrol-electric hybrid which can be connected to mains electricity to recharge the batteries. This increases the electric-only running range, meaning most journeys of around 30 miles or less will not use the combustion engine at all.

Road Tax (VED) – The annual fee required to obtain a windscreen tax disc. This ‘Vehicle Excise Duty’ is now based on cars’ CO2 emissions: those emitting less CO2 pay less annual road tax. Big changes to road tax rates are due in March 2009 so you should check to see if you’re going to be affected.

Super Fuels – A bit like higher-strength spirits, these fuels often claim to give more ‘bangers per buck’ improving both economy and performance. They cost more at the pumps, but Which? remain unconvinced by their short-term benefits.

The Which? Complete Guide to Greener Driving is available in selected WH Smith, Borders, Sainsbury’s, Tesco and Asda stores for £6.99. The Guide reviews the top 100 eco cars and is packed with practical advice on greener driving.

Do you drive a 'green' car? What are the benefits of driving a green car?

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