Two belts run in oil on this engine: the timing belt and the belt of the oil pump, and the two are changed together. The rubber of the belt breaks down from contamination of the oil, and the main contaminant is fuel: a particulate filter regeneration that does not complete mixes diesel into the engine oil, and that attacks the rubber of the belt.

A disintegrating belt sheds fibres and pieces of rubber into the oil. These block the oil pick-up, the filter and the pump itself, the flow of oil drops and the engine is left without lubrication. From there the crankshaft bearings and the turbo go first, and in the end the engine can even seize.

Time matters more here than mileage. Real failures come between 60 000 and 100 000 miles, that is between roughly 96 000 and 160 000 kilometres, and at three to seven years of age. That is much earlier than the maker's original guidance, which was ten years or 150 000 miles. In 2024 the maker brought this down of its own accord to six years or 100 000 miles, and the reason given was exactly the early wear caused by oil dilution.

The belt runs in oil under the cover, so it cannot be seen from outside, and the beginning of the breakdown is hard to spot without a detailed inspection. What can be seen is the rubber particles and unusual debris appearing in the old oil drained at an oil change. The replacement, with the belts, the tensioners, the idlers and a flush of the lubrication system, costs between 1000 and 1300 pounds.