W10 BMW M5 Prototype Auction Could Fetch £300,000

A remarkable BMW E39 M5 fitted with Volkswagen’s experimental 5.0-litre W10 engine is heading to auction, having once been driven by the late Volkswagen chairman Ferdinand Piëch.

The unusual prototype was created during the E39 M5’s reign as one of the defining performance saloons of its era. Rather than developing a conventional Volkswagen test car, Piëch commissioned an engineering project that placed the experimental W10 beneath the bonnet of a BMW M5.

The naturally aspirated 5.0-litre engine produces 473bhp and 437lb ft of torque, giving it a substantial advantage over the standard BMW S62 V8, which developed 394bhp and 369lb ft. Power is sent through a six-speed manual gearbox to the rear wheels.

According to Broad Arrow Auctions, the prototype delivers a more immediate and unfiltered driving experience than any production M5 offered at the time. Its traction control, stability control and ABS systems were also deactivated, making this considerably more than an engine-swapping exercise.

The project was reportedly a personal request from Piëch rather than an official Volkswagen programme, with costs said to have reached around €2 million. Piëch himself drove the finished car, which remains fully usable despite its experimental origins.

Much of the original E39 M5 interior remains in place, although the prototype has an aftermarket dashboard without an odometer. As a result, its total mileage is unknown. The current owner acquired the car around a decade ago and has continued to drive it, with the BMW receiving servicing as recently as 2025.

Broad Arrow expects the car to sell for between £215,000 and £300,000 (€250,000-€350,000) at its forthcoming Belgian auction. That estimate could attract serious attention given the engine’s extreme rarity.

Only three W10 engines were reportedly built, according to Sabine Willeke, one of the engineers involved in the project. One remains in Germany, another sits in this E39 M5, while the third is being offered separately as a display engine.

For BMW collectors, it is an extraordinary combination: one of the most recognisable M5s ever built, transformed by a secretive Volkswagen engineering project and once driven by one of the most influential figures in the German motor industry.