The comparative statistics in the tables are taken from the joint DfT/HMT consultation 'Road fuel gases and their contribution to clean low-carbon transport' released in June 2003.
Several sources of uncertainty arise when assessing the performance of LPG vehicles. The level of emissions improvement in LPG cars depends heavily on the particular engines and conversions involved and on the standard of conversion. For these reasons, absolute comparison of LPG and conventional cars is not possible. The table gives an indication of the comparative figures.
|Diesel (g/km)||Petrol (g/km)(10)|
|Conventional fuel cars—EU emission limits|
|Euro III—mandatory from 2001||0.50||0.05||0.15|
|Euro IV—mandatory from 2006||0.25||0.025||0.08|
|LPG cars—indicative performance(11)||LPG NOx (g/km)|
|2002–03—typical powershift approved aftermarket conversion||n/a||n/a||0.123|
|2002–03—typical OEM ('Original Equipment Manufacturer') LPG car||n/a||n/a||0.035|
(10) No PM limits for petrol or LPG vehicles, since emissions are very low.
(11) Data provided by Energy Saving Trust
Compressed natural gas is primarily used as an alternative fuel for heavy goods vehicles. The following table was included in the road fuel gas consultation document and shows the comparative performance of a natural gas version of one widely used vehicle, compared to EU diesel standards.
|Emission limits||Test cycle||NOx||PM10|
|Euro III||(13)ETC||5||(14)0.16 and 0.21|
|Natural gas vehicle|
|CNG Scania vehicle(15)||ETC||0.96||0.007|
(12) http://europa.eu.int/comm/enterprise/automotive/pagesback/ pollutant emission/pollutant.pdf
(13) European Transient Cycle
(14) For engines having a swept volume of less than 0.75 dm3 per cylinder and a rated power speed of more than 3,000 min-1
(15) CNG Emission Tests based on Scania re-engineering programme Millbrook Vehicle Emissions Laboratory g/kwh