Manufacturers quote service intervals from 10,000 up to 20,000 miles. Those figures assume the kind of driving the engine was designed around — and plenty of UK driving is not it.
What shortens the interval
- Short journeys where the engine never fully warms through, so fuel and water stay in the oil
- Stop-start town traffic, where hours accumulate faster than miles
- Towing, roof boxes and heavy loads
- Diesels doing mostly short runs, where the particulate filter regenerates often and dilutes the oil
A practical rule
If most of your driving is short and urban, treat the long-life interval as optimistic and change annually, or at half the quoted mileage. Oil is cheap. Engines are not.
Do not forget the filter
Change the oil filter every time. A new filter with old oil, or old filter with new oil, defeats the point — and the capacity figure with the filter included is the one to buy to.