The brief
The owner had been finding fresh oil spots on his driveway every morning. The dipstick kept showing a slow drop between checks. He brought the A6 in to find the source before the next service was due.
A slow oil leak is easy to ignore by topping up, but the spots and the dropping level were both telling the same story: oil was getting out somewhere, and it would only get worse. Better to find it now, while it is a manageable repair, than to let it run until the level drops far enough to matter.
The diagnosis
On the lift, the leak point was clear: the sump pan had a hairline crack at one corner. Almost certainly from a previous undertray strike, the kind of speed-hump or kerb hit that flexes the pan and starts a fatigue crack at a stress point.
The gasket was actually still holding the joint sealed. The crack itself was the leak path. So this was not a re-seal job, where you drop the pan and fit a new gasket. It was a pan replacement, because a cracked pan keeps leaking no matter how good the gasket is.
The work
Drained the engine oil, supported the engine, and dropped the failed sump. Cleaned the block face back to bare metal, since any leftover gasket material there would stop the new pan sealing flat.
Fitted a new VAG-spec sump pan with a fresh gasket and new bolts, torqued in the correct pattern so the pan pulls down evenly against the block. Refilled with the correct oil spec.
Then held the engine at idle and checked underneath for any weep before the car went out. A leak fix you do not verify under running pressure is a leak fix you might be doing again next week.
The outcome
No drips overnight. Oil level holding cleanly between checks. No warning lights.
The A6 went home with the underside dry and the source of the slow loss closed off. For the owner, that means no more oil spots on the driveway, no more topping up between services, and an engine that always has its full charge of oil rather than running low.
Catching a cracked pan at this stage is the cheap version; running an engine low on oil is the expensive one.
