The Government publishes a broad range of information on their performance and emissions. To help consumers to make an informed choice when buying a new car, on fuel costs and environmental impact, the Vehicle Certification Agency produces guide lists. These estimate the fuel consumption, carbon dioxide (CO2), and other emissions performance figures of new cars, currently on the market in the UK. An electronic version of the latest edition has been provided to the House Library.
The Department for Transport produces a range of statistics on air quality and other emissions by mode and vehicle as part of the energy and environment datasets (TSGB03) on the gov.uk website. We do not publish comparative data on the air quality emissions associated with different fuel types. Information on all sources of air pollution can be found in the National Atmospheric Emissions Inventory at http://naei.defra.gov.uk/. Progressively tighter emission standards are reducing pollutant emissions from all vehicles.
The Department of Energy and Climate Change also publishes weekly, monthly and annual typical prices of road fuels and petroleum products on the gov.uk website. This data includes super unleaded and non-premium unleaded petrol, and diesel.
The greenhouse gas emissions associated with diesel and petrol will vary depending upon the source of the materials and process used to produce both the fossil and renewable content of the fuel. The Department does not hold information on the carbon dioxide emissions associated with fossil diesel and petrol, and premium and non-premium grades. However, the Renewable Energy Directive sets a default energy content of 32 megajoules per litre for petrol and 36 for diesel, and a greenhouse gas emission of 83.8 grams of CO2 equivalent per megajoule - this equates to atypical emission per litre for petrol of 2681.6 grams of CO2 equivalent and 3016.8 grams of CO2 equivalent per litre for diesel.
Through the administration of the Renewable Transport Fuel Obligation the Department collects information on the carbon and sustainability characteristics of the renewable content of fuel reported under the scheme. This data is published quarterly on the gov.uk website. The latest published data covering the period 15 April 2014 to 14 April 2015, shows that bioethanol, blended with petrol, delivered greenhouse gas savings of 62% compared to fossil fuels and biodiesel, blended with diesel, achieved 75% greenhouse gas savings. The figures exclude emissions from indirect land-use change.
Super unleaded petrol, the premium grade, has a separate specification to regular unleaded petrol. This limits the oxygen content and a higher minimum for octane number. Some vehicles could be more fuel efficient when using this petrol if they have been designed to respond to using such a fuel as they will be able to develop more power from the fuel. While diesel may be marketed as premium on the basis of additives to the base fuel, all diesel is supplied to one standard EN590.
The Department does not have any information regarding the comparative fuel efficiency between super and regular unleaded petrol. However, the influence of fuel upon mileage, is much smaller, in general, than is the influence of other factors such as the vehicle itself (for example, its size, weight, power) , the way that the vehicle is driven, and the road conditions (for example motorway or urban driving).