The brief
This A8 checked in for two things, an oil leak and an air suspension that wasn't holding the car up the way it should, the compressor working overtime. While it was in, the inspection turned up worn air struts as well, so it became a three-part job rather than a return trip later. The oil leak: a common one on these is the oil filter housing gasket, which hardens in the heat over the years and weeps oil down the block. The air suspension: the A8 rides on air struts at each corner, kept inflated by a compressor, and as the struts age the rubber bags leak air, which makes the compressor run constantly to keep up, until the compressor itself wears out from the workload. A leaking gasket, a worn compressor and tired air struts all stay broken until they're replaced, so doing them together was the sensible call.
The diagnosis
The check found the oil coming from a hardened oil filter housing gasket, the air suspension compressor worn out from running constantly, and the air struts leaking air at the bags, the slow leaks the compressor had been fighting. The rest of each system was sound. That's an oil filter housing gasket replacement, a new air suspension compressor, and renewed air struts, the whole picture dealt with in one visit rather than piecemeal.
The work
The oil filter housing was unbolted, the hardened gasket replaced with a fresh genuine Audi-spec gasket and the housing torqued back down, the oil filter renewed and the area cleaned. The worn air suspension compressor was replaced with a new genuine Audi-spec unit, and the leaking air struts renewed, the system bled of air, the ride height calibrated, and any suspension faults cleared. A road test confirmed the engine dry, the car sitting at the right height, the compressor cycling normally rather than constantly, and a composed ride.
The outcome
No oil leak, the engine dry, the car sitting level at the right height, the air compressor cycling normally instead of running flat out, a smooth ride, and no warning lights. The A8 went home with the lot sorted in one go. Catching the worn struts during the inspection saved a second trip, which is the point of going through the whole car rather than just the two faults it came in for.