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Cars and fuel options

This guide contains data on vehicles running on petrol and diesel, as well as ‘alternative’ fuels, such as Liquefied Petroleum Gas (LPG) and Compressed Natural Gas (CNG), and hybrid and electric vehicles.

The different fuels have different merits from an environmental perspective. Compared to petrol, diesel vehicles have significantly lower CO2 emissions per kilometre travelled because of the higher efficiency of diesel engines, and hence have a lower, though still significant, impact on climate change. Diesel vehicles also emit lower levels of CO and HC than equivalent petrol vehicles. However, diesel engines emit greater levels of NOx than new petrol vehicles. As mentioned earlier, emissions of NOx are an air quality issue, particularly in urban areas.

LPG and CNG cars are generally converted from petrol-fuelled cars, either by the original manufacturer or by an aftermarket converter. For practicality, CNG and LPG cars tend to be bi-fuel, meaning that they can run on either petrol or the gaseous fuel. LPG vehicles tend to fall between petrol and diesel in CO2 performance. This is due to the lower carbon and higher energy content by mass of the fuel. CNG offers even lower CO2 emissions than LPG, typically comparable with that of diesels. Local pollutant (CO, HC, NOx and particulate matter) emissions performance of well-engineered LPG and CNG vehicles is similar to that of a petrol vehicle.

Sustainable biofuels also offer a way to reduce the impact of vehicles on climate change. The fuels are not entirely CO2 neutral because of the energy used to grow and process crops, but they can offer substantial CO2 savings over fossil petrol and diesel. Today, most biofuels are sold in blends of up to 5% in fossil petrol and 7% in fossil diesel. These blends are suitable for use in nearly all vehicles.  Some manufacturers offer 'flexi-fuel' vehicles that can run on bioethanol blends up to E85 - a blend of 85% bioethanol with 15% petrol - as well as fossil petrol. Some manufacturers also allow the use of higher blends of biodiesel in their vehicles (check with your vehicle manufacturer). It is important that only high quality biodiesel meeting the European quality standard - EN 14214 - is used.  Blended fuels produced to the EN228 or EN590 standards will contain high quality biofuel as a matter of course.  Further Information on biofuels, and a guide to alternative fuels, can be found on the Energy Saving Trust (EST) website

Hybrid vehicles usually combine an internal combustion engine with an electric motor and battery. There are various ways in which hybrid vehicles can operate. For example, the vehicle may be able to operate solely on its engine, solely on battery power, or on a combination of the two with the battery providing additional power during acceleration and high load conditions. The battery can then be recharged by the internal combustion engine or from energy absorbed during braking or, in some cases, from an external electrical supply. Hybrid vehicles can offer reduced fuel consumption and CO2 emissions, and potentially some reduction in emissions of local pollutants, especially in stop-start motoring. 

Plug-In Vehicle (PIV) is the term for any vehicle that is powered, either in part or in full, by a battery that can be recharged by plugging into an external electricity supply. This includes those that run purely on electricity (pure-electric) and plug-in hybrid electric vehicles.

This guide includes those cars that use a combination of a conventional petrol or diesel engine and battery propulsion. These are known as ‘petrol-electric hybrid’, ‘diesel-electric hybrid’.  Cars that run purely on electricity are also listed in the guide but, since they do not use liquid fuel or emit CO2 while being driven, there is no data given for the fuel consumption or CO2 emissions of pure electric models.

With the range of vehicle fuel technologies now available, it can be difficult to understand which might be the most appropriate.  The Energy Saving Trust has produced an animation to help navigate around all these technologies:

To find out more about electric vehicles, models available and how to get a government grant, visit

Link to Information on Car Fuel Data and CO2 emissions - next page