Cars and Fuel Options

This page contains data on vehicles running on Petrol and Diesel , as well as Biofuel, hybrid vehicles, Liquefied Petroleum Gas(LPG) and  Compressed Natural Gas (CNG) . The different fuels/engines have different merits from an environmental perspective. 

Petrol and Diesel 

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 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 and Particles than new petrol vehicles. As mentioned earlier, emissions of such pollutants are an air quality issue, particularly in urban areas.


Biofuels also offer a way to reduce vehicles' impacts 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 regular petrol and diesel. Today most biofuels are sold in a blends of up to 5% with regular petrol and diesel. These are suitable for use in all vehicles. Fuel standards may be extended in the future to allow more than 5% if it is concluded that this is compatible with existing vehicles. 

Some manufacturers offer 'flexi-fuel' vehicles that can run on bioethanol blends of up to E85 - a blend of 85% bioethanol and 15% petrol, as well as regular petrol. Bioethanol is produced from sugar beet and wheat through a process of hydrolysis, fermentation and distillation. There are currently limited fuel retailing sites that offer this fuel, but the number is set to grow in the future. A list of Irish biofuels suppliers can be downloaded here from our website.  

Some manufacturers also allow the use of higher blends of biodiesel in their vehicles (check with your vehicle manufacturer). Biodiesel is produced from pure plant oil, recovered vegetable oil or beef tallow. These feed materials are converted by a trans-esterification process, which involves the use of methanol (or ethanol). Biodiesel and a glycerol coproduct are produced. Biodiesel which meets the standard EN 14214 can be blended with mineral diesel in a mix of up to 5% biodiesel and used as a fuel in a standard diesel vehicle. It is important that only high quality biodiesel meeting the EU quality standard - EN 14214 is used.

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LPG and CNG cars are generally converted from petrol fuelled cars, either by the original manufacturer or an aftermarket converter. For practicality, CNG and LPG vehicles tend to be bi-fuel, meaning 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 diesels. Local pollutant (CO, HC, NOx and Particles) emissions performance of well engineered LPG and CNG vehicles is similar to a petrol vehicle or slightly better.

Hybrid vehicles

Hybrid vehicles combine an internal combustion engine with an electric motor and battery. There are various ways in which hybrid vehicles can operate. For example the electric motor can be used to provide 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. Hybrid vehicles offer reduced fuel consumption and CO2 with potentially some reduction in emissions of local pollutants. 

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