Fuel consumption and emissions

How car choice affects the environment - and your pocket

You can do your bit to help preserve the environment by choosing a car that uses less fuel and produces fewer toxic emissions. Cars that use less fuel will be cheaper to run as well.

Size Matters

Buy the right car for your needs. People carriers make sense if you're going to use all the seats. But a smaller car is more economical if there's just one or two of you.

Weight Matters

How much your car weighs is key to how much fuel it uses. In fact, weight is more important than engine size – a heavy car needs a lot of fuel to get it going from a stop but a big engine in a small car can be economical.

Manual, automatic or automated manual?

For a smooth drive around town, it's tempting to opt for an automatic but the choice of transmisison you make can have a big affect on fuel consumption.

Traditional Automatics may use around 10% more than manuals whilst cars with a constantly variable transmission (CVT) use around 5% more.

More and more cars are now being offered with 'automated manual' transmissions – clever hydraulic and electronic systems take care of the clutch operation and gear changes to offer a fuel consumption saving compared both with more conventional autos and even manual transmissions.

Modern semi-automatic features such as button- or paddle- operated gear changes and automatic clutch control can help you to use less fuel.

At motorway speeds fuel consumption evens out and there's not much difference between manuals and automatics of any type.


Fuel consumption will be around 4% higher than for a two–wheel drive with the same style body. If you compare a four-wheel drive with the most economical vehicle that can carry the same load, the fuel consumption could be up to 14% higher for the four–wheel drive.

As with any class of car there are good and bad performers though – if you need a 4x4 then try to choose one of the more fuel efficient models.


All vehicles give out carbon dioxide (CO2) the main gas behind climate change. The amount produced is directly related to fuel consumption which is why car manufacturers are doing so much to improve new car fuel economy and why car tax rates are based on official CO2 emissions figures.

All vehicles produce toxic emissions such as nitrogen oxide(NOx) as well but there's less you can do to affect this other than trying to run the newest car you can.

New car models must undergo a wide range of safety and environmental tests as part of the official Euopean 'type approval' process. These include tests to make sure that exhaust emissions meet European standards which have been getting more stringent since the early 1990s.

The so-called Euro I standard came into force in 1992 and the limits this set for a petrol car could effectively only be met by fitting a catalytic converter in the exhaust system.

Each new standard is tougher than the last. We're now up to Euro V which came into force in 2009 and – like the 1992 standard and Catalytic converters on petrol cars – this effectively requires all new diesels to be fitted with a Diesel Particulate Filter in the exhaust.

The newer the car, the better for the environment. One pre-1992 car without a catalytic converter gives out roughly the same toxic emissions as 20 of today's new cars.

Fuel Choices

Petrol cars use more fuel than diesel, giving out around 10% more carbon dioxide (CO2). But petrol cars produce fewer toxic emissions.

Diesel cars use less fuel than petrol cars, so give out less CO2. Direct-injection diesel engines give the best fuel economy. Depending on the type of driving you do diesels may not be a good choice for other reasons.

LPG gives off lower toxic emissions than Diesel and pre Euro IV petrol engines, but fuel consumption is worse.

Taxes and Charges

The price of Road Tax increases with the car's official CO2 emissions, so it pays to get a smaller, more economical car.

Company Car Tax is also based on the amount of CO2 your car emits. The less CO2 your car emits, the less tax you pay. There is a 3% surcharge for diesel cars because of their higher toxic emissions.

Some cars with very low CO2 emissions that also meet the Euro V emissions standards benefit from the Greener Vehicle Discount under the London Congestion Charge Scheme.

Going Green in a Nutshell

  • Opt for the smallest car that suits your needs
  • The less fuel you use, the less you pollute
  • Newer cars are generally better for the environment
  • Road tax is based on the amount of CO2 your car emits
  • Manual cars generally use less fuel than automatics
  • LPG and diesel give out less CO2 than petrol cars
  • LPG and petrol cars give out fewer toxic emissions than diesels
  • Cars with very low CO2 emissions get a discount on the London Congestion Charge
  • The way you drive your car can affect the amount of fuel you use

29 July 2011