Generally, cars with smaller engines are cheaper to run, produce less pollution and cost less on your Churchill car insurance – so they are a good bet all round for the eco-conscious motorist.

The government recently launched a website (www.dft.gov.uk/ActOnCO2) in connection with What Car? magazine to inform buyers of the greenest models in each class of vehicle. For example, the Volkswagen Polo Blue Motion is the least-polluting car in the ‘supermini’ class, producing just 99g of CO2 per km.

In the small family car class, the Toyota Prius tops the government’s green list. This popular hybrid model saves fuel by employing an electric motor to help the regular petrol engine when accelerating. The electric motor then recharges itself while the car is driving at a constant speed.

If an executive car, or a large family car, is the only thing for you, the new government website can still help you choose the greenest model available. In the executive car class, for example, the BMW 5 Series E60/E61 heads the list, producing 136g of CO2 per km. And the greenest estate car? The Skoda Fabia Estate.

Even those vilified 4x4s have different shades of green. The least polluting large 4x4, for example, with its 2.2 litre diesel engine, is the Hyundai New Santa Fe.  In fact, diesel engines frequently perform better than petrol engines in the green stakes as they are more efficient with their fuel. 

There are other less environmentally harmful fuels appearing on the market, though they can sometimes be a little hard to find at the pumps:

• Liquefied petroleum gas produces fewer emissions of carbon dioxide, hydrocarbons, carbon monoxide and nitrous oxides than both petrol and diesel (source: www.petrolprices.com).
• Compressed natural gas (CNG), meanwhile, is more efficient, operates quietly and emits fewer toxic chemicals than conventional fuels. Many petrol and diesel engines can be converted to run on CNG.
• Bio-diesel, another alternative fuel, has been causing heated debate amongst environmentalists for some time. It is produced from renewable sources such as sugar beet, rapeseed, palm oil and sunflowers, and it is carbon-zero (as all the carbon dioxide it produces is absorbed by the plants used to make it).

It sounds like the perfect green fuel. However, there are concerns that vast amounts of rainforest or arable land will need to be cleared to grow the raw materials if it becomes too popular.

Less pollution means a healthier, more pleasant world. A smaller engine also means lower costs, both on fuel and on the price of your Churchill car insurance.