Every now and then, we receive spy photos that raise more questions than answers. Such is the case with this Audi S6 caught in northern Europe during the last days of winter testing. It appears to be a US-spec car judging by the orange markers in the headlights, but it's the back that looks puzzling. We're not talking about the missing reflector on the passenger side as the exhaust makes us scratch our heads trying to figure out what's going on.

The ghastly fake tips of the normal A6 have remained intact, but the test mule has two real exhaust tips mounted closer to each other near the center. You won't find that on the European-spec S6 where the typical quad exhausts of an S model are split into two on both corners of the rear bumper. Mind you, Audi sells the S6 on the Old Continent with a diesel engine and hides the real exhaust on the left side where there are two tips. The visible ones are all decoys, which isn't the case in the US and other countries where what you see is what you get.

Audi S6 test mule spy photos

Then there's the protuberance underneath the rear bumper on the driver's side. It appears to be some sort of box you won't find on the other side. Your guess is as good as ours as to what Audi is testing, but we're getting the impression the S6 was used primarily for its body. In other words, the Four Rings could be testing a new piece of hardware that might not necessarily go into the BMW 5 Series competitor.

The vehicle rides unusually low, even for an S6, and our spies have told us the car was unusually loud. Since it had the orange side markets, perhaps it was the gasoline-fueled version rather than Europe's oil-burner with its 3.0-liter TDI V6. Whatever this is, the peeps from Ingolstadt are surely up to something and it involves a good ol' engine.

We'll remind you that the German luxury brand has ended the development of internal combustion engines and will launch its final new ICE-powered car in 2025. Eight years later, production of piston-powered cars will come to end, except in China where Audi has said it might continue with conventional powertrains depending on local demand.

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