Yes, It’s BMW M5 Volkswagen
From the outside, it looks like a fairly ordinary E39 BMW M5. Carbon Black paint, four doors, familiar wheels and quad exhaust tips give away little about what is hiding underneath the hood. But this particular M5 was not built to BMW specifications. Sometime around the turn of the millennium, its celebrated V8 was removed and replaced with an experimental Volkswagen W10. On October 9, the strange prototype is scheduled to cross the auction block in Belgium, bringing one of Volkswagen’s most secretive engineering projects back into public view.
The story leads directly to Ferdinand Piëch, the famously ambitious executive who transformed Volkswagen Group while pursuing engineering projects that sometimes seemed almost impossible. Volkswagen was experimenting heavily with compact multi-cylinder engines during this period, eventually putting W8 and W12 engines into production and developing the extraordinary W16 used by Bugatti. Somewhere in that family tree was a naturally aspirated 5.0-liter W10 producing 480 PS, or roughly 473 horsepower. According to Broad Arrow, only three W10 engines were built.
There was one obvious problem: Volkswagen did not have the right car in which to test it. Rather than build an entirely new development car, the company reportedly chose one of the best performance sedans in the world. A BMW E39 M5 was purchased, stripped of its original V8 and transformed into a Volkswagen test mule hiding in plain sight.
Why Put a Volkswagen Engine in a BMW?
The M5 began life as a normal BMW, built in March 1999 with the 4.9-liter S62 V8 and six-speed manual transmission that helped make the E39 one of the most celebrated sports sedans ever built. For Volkswagen’s experiment, the BMW engine came out and the prototype W10 went in. The M5’s six-speed manual remained, but much of the car was adapted around the experimental powerplant, including a replacement Stack instrument cluster and additional gauges mounted inside the cabin.
The W10 displaced 5.0 liters and produced 480 PS and 592 Nm of torque, or about 437 lb-ft. That gave it considerably more power than the standard E39 M5. Broad Arrow says the car was commissioned during Piëch’s tenure at Volkswagen and used by him as personal transportation while the engine was being developed. ABS, traction control and stability control were also disabled during the conversion, leaving the prototype considerably less civilized than the BMW that originally left the factory.
The project never resulted in a production Volkswagen W10. Instead, Volkswagen continued developing its unusual W-engine family in other directions. The W8 eventually appeared in the Passat, W12 engines powered models from Volkswagen, Audi and Bentley, and the concept reached its most extreme form with the Bugatti Veyron’s W16. This strange BMW therefore survives as a rolling branch of Volkswagen history that might easily have disappeared completely.
For Years, Almost Nobody Knew Where It Went
Once Volkswagen finished developing the W10, the unusual M5 largely disappeared from public view at a time when many car companies were attempting to build supercars. The engine never entered production and little official information about the project was released. For years, the idea that Volkswagen had secretly installed an experimental ten-cylinder engine into a rival manufacturer’s performance sedan sounded more like an enthusiast rumor than a documented factory project.
The car began attracting attention again after an incomplete Volkswagen W10 surfaced in Germany in 2023. Details on that engine reportedly corresponded with the unit installed in the M5, while Volkswagen confirmed the involvement of the German company that had carried out the conversion. The complete car later appeared through a Belgian specialist and proved that the unlikely prototype had survived. Better still, it remained drivable. Its current owner registered it in Slovakia and continued using the car rather than hiding it away in a collection.
Now the M5 has emerged in public for an entirely different reason. Broad Arrow will offer it as Lot 164 at the Zoute Concours Auction on October 9, 2026, with an estimate of €250,000 to €350,000. The sale also includes a second Volkswagen W10 mounted on a display stand. There are faster M5s and more valuable Volkswagens, but perhaps none with a stranger story: a secret Volkswagen prototype wearing BMW badges, powered by an engine that never officially made it into a car, then virtually disappearing for decades before finally resurfacing.
