Choosing a vehicle

When choosing a vehicle, try to bear in mind economy and emissions.

Try to choose a vehicle with low fuel consumption and low emissions. The Vehicle Certification Agency produces a guide to the fuel consumption of new vehicles.

Manual versus automatic

In the past, vehicles with automatic transmission were generally less fuelefficient than those with manual transmission. However, recent improvements in technology have resulted in much more fuel-efficient automatic vehicles.

Now, some automatic vehicles are more economical and have better emission statistics than their manual counterparts. As with manual vehicles, check the carbon-dioxide and fuel-economy statistics when choosing an automatic.

Petrol engines

There are advantages and disadvantages to all types of fuel. To help you make an informed choice and understand the effect each has on the environment, some of the differences are explained below.

The modern petrol engine has been designed to operate more efficiently to meet increasingly stringent emissions standards.

Key factors in this improvement in reducing exhaust pollution are

• fuel injection
• electronic engine management systems
• redesigned exhaust systems.

Ever stricter controls on exhaust emissions require catalytic converters to be fitted to the exhaust systems of all new petrol-engined vehicles.

Catalytic converters

These are exhaust-treatment systems that remove up to 75% of carbon monoxide, nitrogen oxide and hydrocarbons.

The converter is a honeycomb-shaped filter with a total surface area about equal to a football pitch. This surface is coated with precious metals such as platinum, palladium and rhodium. These speed up a chemical reaction in the exhaust gases as the engine heats up.

The oxygen content of the exhaust is monitored and a sensor triggers controls to adjust the air–fuel mixture.

The converter only deals with toxic and polluting gases. Carbon dioxide is still produced.

Leaded petrol can’t be used in vehicles fitted with a catalytic converter. Even one tankful can permanently damage the system.

If you over-accelerate or exceed 3000 rpm, the catalytic converter can’t clean up emissions completely and will release some that are contaminated. Make sure, therefore, that you don’t drive in such a way that this will occur.

Diesel engines

These engines are very fuel-efficient and produce less carbon dioxide than any other road transport fuel.

Compared with petrol-engined cars, they also emit less carbon monoxide and fewer hydrocarbons. They do, however, produce more emissions of nitric oxides and particulates that are bad for local air quality.

Newer vehicles have to meet strict new emissions standards aimed at reducing these pollutants.

New fuels

All road fuels sold in the EU now have a very low sulphur content. They’ve been specially formulated to meet EU laws concerning the use of this chemical.

Sulphur is the main component of particulates in exhaust emissions, and it also produces acidic gases. The lower sulphur content in these fuels helps to reduce this source of pollution.

More advanced fuels are still becoming available, and motorists should always consider using the most up-to-date type of fuel for their vehicle.

Liquefied petroleum gas

Vehicles powered by liquefied petroleum gas (LPG) are now commercially available and the number of fuel stations supplying LPG is increasing steadily. This fuel is cheaper to use than petrol or diesel and the emissions cause less air pollution. However, LPG does produce more carbon dioxide per mile travelled than diesel.

Electric and hybrid vehicles

Manufacturers are offering an increased choice of electric and hybrid vehicles, which offer reduced local pollution and lower running costs. Hybrid vehicles can also help overcome the worry about running out of power that’s associated with driving an electric car for a long distance.