The essentials
- Short trips in town clog the particulate filter.
- Once a week a twenty-minute run on open road clears the filter.
- Bad fuel costs the high-pressure pump far more than the price difference.
What short trips do
A diesel engine wants long, warm runs. Use it only for two kilometres in town and the particulate filter clogs until one day you stop.
How the diesel lasts longer
- As a rule of thumb, a twenty-minute run on open road once a week clears the filter.
- Fill up where you know the station. Bad fuel costs the high-pressure pump far more than the price difference.
- If the filter light comes on: do not ignore it and do not have it "removed". Without the filter the car fails inspection.
- Cambelt or chain at the maker’s interval — on older engines this is the failure that ends the engine in one go.
If you drive under ten thousand kilometres a year, mostly in town, petrol works out cheaper overall — despite the higher consumption.