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Implications of the growing popularity of diesel vehicles
From an environmental and health perspective, the increasing size and age of the diesel fleet are growing problems for New Zealand.
A diesel vehicle of a given engine size is more fuel efficient (by about one-third) and produces fewer greenhouse gas emissions than a petrol engine of equivalent size. However, in 2007, the average engine size of light diesel vehicles entering the fleet was 2.8 litres, compared to 2.2 litres for petrol vehicles. As a result, the efficiency gains of diesel engines are often offset by increased engine size.
Older diesel engines can also produce significant levels of exhaust particulates – 72 per cent of all diesel vehicles in New Zealand are more than seven years old. In 2007, 6 per cent of the vehicles entering the fleet were used diesels. These vehicles may emit higher levels of pollutants than their newer counterparts. However, the Vehicle Exhaust Emissions Rule, which took effect at the beginning of 2008, will limit the importation of these older vehicles.
Improvements in exhaust emissions control technology mean new diesel vehicles with small engines, manufactured to the latest emissions standards, can have a less damaging effect on the environment. They produce low levels of harmful exhaust emissions and fewer greenhouse gas emissions than their petrol counterparts. In 2007, 11 per cent of the vehicles entering the light fleet were brand new diesels, and 2 per cent had engine sizes under 2.25 litres.
Vehicles entering the light vehicle fleet by engine size in New Zealand, 2007
Data source: Ministry of Transport.
Vehicles entering the light vehicle fleet by engine size, 2007
| Engine size (litres) | NZ-new petrol | Used petrol | NZ-new diesel | Used diesel |
|---|---|---|---|---|
| < 1 | 384 |
1692 |
3 |
2 |
| 1 - < 1.25 | 494 |
703 |
55 |
0 |
| 1.25 - < 1.5 | 9728 |
25024 |
264 |
7 |
| 1.5 - < 1.75 | 4945 |
6919 |
234 |
10 |
| 1.75 - < 2 | 19788 |
49570 |
3196 |
343 |
| 2 - < 2.25 | 536 |
3321 |
978 |
536 |
| 2.25 - < 2.5 | 15267 |
16928 |
4581 |
961 |
| 2.5 - < 3 | 3245 |
7012 |
14145 |
9049 |
| 3 - < 4 | 16556 |
3771 |
1689 |
1974 |
| 4+ | 4321 |
3055 |
628 |
414 |
Data source: Ministry of Transport.
This information has come from the environmental report card on vehicle kilometres travelled by road.
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Last updated: March 2009
