- Broad Arrow will auction the prototype E39 M5 at Zoute Concours in Knokke-Heist on October 9, 2026, estimated $285,000–$400,000.
- The naturally aspirated, all-aluminum 5.0-liter W10 is rated at 473 hp.
- Only three Volkswagen W10 engines were ever built.
Only one road-going car has ever carried a Volkswagen W10 engine, and it wears an E39 BMW M5 body. Broad Arrow Auctions will offer the prototype at its Zoute Concours sale in Knokke-Heist, Belgium, on October 9, 2026, carrying an estimate of €250,000 to €350,000 (about $285,000 to $400,000).
Ferdinand Piëch, then Volkswagen's chairman, ordered the swap in 1999 as an off-the-books project. His engineers pulled the factory S62 V8 from a 2000 M5 and dropped in an experimental engine built for a job BMW never signed up for.
Gallery: 2000 BMW M5 Volkswagen W10 Prototype
The One-Off Car Headed To Auction
Piëch, who took over a Volkswagen on the edge of bankruptcy in 1993, pushed an engineering-first approach across the brand. According to Broad Arrow, Piëch told his engineers in 1999 to build a W10 for a high-performance sedan, at a time when neither Volkswagen nor Audi had anything to answer the M5 with.
Rather than build a bespoke test mule, the team fitted the W10 straight into an E39 M5 chassis, dated to March 2, 1999, keeping the car's six-speed manual gearbox. Finished in Carbon Black Metallic over black leather, chassis WBSDE91040GJ16436 looks like any other M5 from outside.
Traction and stability control were switched off, along with the anti-lock brakes, with a stand-alone ECU running the engine instead. The standard instrument cluster gave way to an aftermarket Stack racing dash with no odometer, so the car's actual mileage can't be confirmed.
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, though the extent of the conversion means it still lacks a certificate of conformity, a detail the next M5 owner will need to sort out.
473 HP From One Of Only Three Examples
The naturally aspirated, all-aluminum 5.0-liter W10 is rated at 473 hp and 437 lb-ft of torque, a direct precursor to the quad-turbo W16 that would later power the Bugatti Veyron. That's 79 hp and 68 lb-ft more than the S62 V8 it replaced.
Ten cylinders sharing a single crankshaft deliver that power with a smoothness few production engines match, while the stand-alone electronics give it sharper, more immediate throttle response than any factory M5 ever offered. It's a strange engineering detour that never went anywhere else.
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 displayed alongside the M5. One powers the car," a detail that makes this M5 the sole surviving example fitted to a road car.
Willeke has also said the car served as Piëch's own personal transportation during its secretive development, built outside Volkswagen's formal R&D structure at a reported cost approaching €2 million ($2.3 million). The project never advanced past this prototype stage, and Volkswagen never returned to the W10 concept once it wrapped.
Motor1's Take: E39 M5 collectors must decide whether unique provenance outweighs factory originality. The buyer will also inherit registration and conformity work, so museums or collectors with access to specialist dealers are likeliest bidders.
A strong sale will push restorers, brokers and specialist dealers to hunt 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.
