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.
- Once a week a twenty-minute run on open road — that 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.