It was due for an oil change anyway. Down to business. Out came 1.5 litres of treacle, black as night.
Unsurprisingly, with 5 litres of fresh fully synthetic in there, the dak-dak was soon banished!
I'd forgotten about the other type of Citroën owner - not the one who nervously checks everything all the time, but the one who spends almost nothing, ever.