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Carbon dioxide (CO2) emissions

Why CO2 is important

Fuel combustion in the engine emits the greenhouse gas carbon dioxide (CO2). CO2 is widely believed to be the main greenhouse gas contributing to climate change. The amount of gas emitted is directly related to the amount of fuel used. The more fuel-efficient your vehicle is, the less CO2 it will produce.

How the ratings are obtained

The CO2 ratings are obtained as follows:

  1. The carbon dioxide rankings are obtained from the fuel economy rankings.
  2. A suitable conversion factor is used to take into account whether the fuel used was petrol (including its octane rating), diesel, LPG, etc.
  3. Stars are assigned to identify the best performers (those with the most stars), the worst performers, and average performers.

Stars are assigned using a similar approach to that adopted by ADR (Australian Design Rules) for their greenhouse rating. In general, a petrol vehicle will receive the same star rating for CO2 as for fuel economy.

Conversion factors

Available vehicle information only specifies the fuel type (e.g. petrol) rather than the octane rating (91, 95 etc). The conversion factor for petrol is based on the average octane rating of fuel sold in New Zealand in 2005.

The conversion factors used are as follows:

  • Premium petrol – multiply the L/100km by 23.414 to give CO2 grams/km
  • Regular petrol – multiply the L/100km by 22.847 to give CO2 grams/km
  • Petrol (average) – multiply the L/100km by 22.961 to give CO2 grams/km
  • Diesel – multiply the L/100km by 26.050 to give CO2 grams/km

Below the ratings on the comparison page you can see the grams/km value and what this means in terms of annual emissions of CO2 from the vehicle.

Please note: L/100km means “Litres per hundred kilometres travelled”. CO2 grams/km means “grams of carbon dioxide emitted per kilometre travelled”.

The annual figure is based on a vehicle traveling 14,000 km over a year.