An E39-generation BMW M5 fitted with a rare Volkswagen W10 engine is scheduled to cross the auction block, offering collectors an unusual piece of Volkswagen engineering history. The road-legal prototype replaces the M5’s familiar S62 V8 with a naturally aspirated 5.0-liter W10.

A unique W10-powered M5

Volkswagen acquired the M5 in 1999 while developing a sedan intended to compete with it. Rather than simply install one of its existing V8 engines, Ferdinand Piëch pursued a more unusual solution: combining two 2.5-liter VR5 five-cylinder engines into one powerplant.

The resulting W10 reportedly produces 480 horsepower and 437 lb-ft (592 Nm) of torque. Volkswagen tested the prototype extensively, and Piëch reportedly used it as his personal vehicle for a period.

Only a small number of W10 engines are thought to have been built. The project reportedly cost about €2 million ($2.27 million) but never reached production. Its development did, however, contribute to Volkswagen’s later W12, which combined two VR6 engines, as well as the W16 used in the Veyron and Chiron, which was based on the VR8.

Manual transmission and rear-wheel drive

This M5 is believed to be the only W10-powered example installed in a road-legal car. In addition to its unusual engine, it retains a six-speed manual transmission and rear-wheel drive.

Broad Arrow Auctions is offering the car on October 9, with an estimated sale price of €250,000 to €350,000 ($285,000 to $399,000). The listing provides a rare opportunity to purchase a vehicle connected to Volkswagen’s experimental engine program.

The car’s mileage is unknown because its original instrument cluster and odometer were replaced. Visible scuffs, scrapes, and stone chips on the front end suggest the prototype has seen substantial use, although the source does not provide a confirmed mileage figure.