The BMW M5 That Swallowed a Secret Volkswagen W10 — And Its Heading to Auction
The BMW M5 That Swallowed a Secret Volkswagen W10 — And Its Heading to Auction
Imagine popping the hood of a classic BMW M5 and finding a Volkswagen engine staring back at you. Not just any Volkswagen engine, mind you — one of only three naturally aspirated W10 units ever built, a direct ancestor of the Bugatti Veyrons quad-turbo W16. Thats exactly the surprise waiting inside a 2000 BMW E39 M5 thats about to cross the auction block.
Broad Arrow Auctions will offer this one-off prototype at its Zoute Concours sale in Knokke-Heist, Belgium, on October 9, 2026. The estimate sits between €250,000 and €350,000 — roughly $285,000 to $400,000. For that money, youre not just buying a car. Youre buying a piece of secret automotive history that was never supposed to see the light of day.
A Chairmans Off-the-Books Obsession
Back in 1999, Ferdinand Piëch was running Volkswagen. Hed taken over the company in 1993 when it was teetering on the edge of bankruptcy, and he pushed an engineering-first philosophy across the entire brand. Piëch had a reputation for demanding the impossible, and this project fits that reputation perfectly.
According to Broad Arrow, Piëch told his engineers to build a W10 engine for a high-performance sedan. There was just one problem: neither Volkswagen nor Audi had anything to compete with the BMW M5 at the time. So instead of building a dedicated test mule, the team took a different route. They pulled the factory S62 V8 out of a 2000 M5 and dropped the experimental W10 straight into the E39 chassis, dated March 2, 1999. The car kept its six-speed manual gearbox.
This wasnt an official Volkswagen R&D program. It was an off-the-books project, built outside the formal structure, at a reported cost approaching €2 million (about $2.3 million). Piëch reportedly used the car as his own personal transportation during its secretive development.
What Makes This W10 So Special
The engine itself is a naturally aspirated, all-aluminum 5.0-liter W10. Its rated at 473 horsepower and 437 lb-ft of torque. Compared to the S62 V8 it replaced, thats an extra 79 hp and 68 lb-ft. Ten cylinders sharing a single crankshaft deliver power with a smoothness that few production engines can match.
Because the car runs a stand-alone ECU, the throttle response is sharper and more immediate than any factory M5 ever offered. Traction and stability control were switched off, along with the anti-lock brakes. The standard instrument cluster gave way to an aftermarket Stack racing dash with no odometer, which means the cars actual mileage cant be confirmed.
Sabine Willeke, who led the engineering team behind the project, told Broad Arrow that only three W10 engines were ever built. “One remains in Germany,” she said. “One is dis played alongside the M5. One powers the car.” That last detail makes this M5 the sole surviving example fitted to a road car.
Looks Like Any Other M5, Until You Look Closer
Finished in Carbon Black Metallic over black leather, chassis WBSDE91040GJ16436 looks completely ordinary from the outside. Youd walk right past it at a car meet. Thats part of the charm. This is a sleeper in the truest sense — a car that hides its secret until you lift the hood or stab the throttle.
The current owner bought the M5 roughly a decade ago through contacts in the engineering world and road-registered it in Slovakia. He drives it rather than storing it in a climate-controlled garage. Thats refreshing, but it also means the car still lacks a certificate of conformity. The next owner will need to sort out that paperwork, which is a detail worth factoring into any bid.
The project never advanced past this prototype stage. Volkswagen never returned to the W10 concept once it wrapped. The W16 that eventually powered the Bugatti Veyron owes a clear debt to this experimental engine, but the W10 itself remained a dead end — a fascinating what-if that only exists in three examples.
Why This Auction Matters Beyond the Car
For E39 M5 collectors, this car presents a genuine dilemma. Do you value unique provenance over factory originality? A standard E39 M5 is already a modern classic, celebrated for its balance, its steering feel, and that glorious S62 V8. This car throws all of that out the window. Its not original, but its never been anything else either. Its a factory-backed experiment that escaped the crusher.
The buyer will inherit registration and conformity work, so museums or collectors with access to specialist dealers are the likeliest bidders. If the sale brings strong money, expect restorers, brokers, and specialist dealers to start hunting for other manufacturer test mules or reworked cars. If the result is modest, one-off prototypes will remain a curiosity rather than a new collector category.
Either way, this M5 represents something increasingly rare in the collector car world: a genuine secret. Not a tribute, not a restomod, not a dealer special edition. A real engineering skunkworks project ordered by one of the most demanding executives in automotive history.
The Takeaway
Before you dismiss this as just another expensive oddity, consider what it represents. Piëch wanted to beat BMW at its own game, and he did it by borrowing BMWs own car. The result is a machine that shouldnt exist — a Volkswagen heart beating inside a BMW body, with a paper trail linking it directly to the man who later gave us the Veyron.
If you had the means, would you park it in a museum or drive it like its current owner does? Thats the question this auction ultimately asks. The answer says as much about you as it does about the car.
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Mike Brown
Mike Brown – One of those authors who helps readers not get lost in today's news flow. He dives into political affairs as well as world events, social trends, and everyday stories that matter to everyone. The main focus of his work is fact-checking, clear language, and the ability to lay out the key points so that the reader gets a comprehensive and reliable picture of the topic in just a few minutes.
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