Ferdinand Piëch, the relentless and brilliant patriarch of the Volkswagen Group, is known for putting out some legendary cars and engines. Under his rule, nothing was too ambitious, too complex, or too strange. That era gave us the W-8, W-12, and W-16 engines. It birthed a V10 TDI Touareg and almost gave us a Bugatti with an eighteen-cylinder engine. And somewhere in that fever dream of innovation, Piëch quietly commissioned something even more unusual: a W10 engine, stuffed into none other than a BMW M5.

The Myth Becomes Reality

For years, the “W10 M5” was little more than internet folklore—an automotive Bigfoot. Some believed Volkswagen had built a ten-cylinder W engine. Fewer believed one had ever been installed in a car. But in 2023, The Drive tracked down what appeared to be the last surviving W10 engine. And then in 2025, DriveTribe finally confirmed what many had suspected: the elusive W10 M5 not only exists—it runs. And it rips.

According to the dyno, the car makes 480 horsepower at the wheels, translating to roughly 530 hp at the crank. That’s more than the stock E39 M5’s S62 V8, which produced 394 hp, and even outguns the next-gen E60’s screaming S85 V10, rated at 500 hp. Not bad for an experimental motor cobbled together over two decades ago.

So… Why? That’s the real question. Why did Volkswagen, of all companies, decide to build a W10 engine and put it in a rival’s car?

At the time, VW didn’t have a true performance sedan. The Audi RS6 was still a niche project. The Porsche Panamera wouldn’t arrive until 2009. If they wanted to benchmark their wild new engine, they needed a car with the right balance of chassis dynamics, space, and subtlety. And the E39 BMW M5? That was the standard.

It wasn’t just good—it was perfect. It had room under the hood. It handled brilliantly. It flew under the radar. And crucially, it came with a six-speed manual transmission, ideal for development. So VW bought one, dropped in their W10 prototype, and began what must have been the strangest case of corporate espionage-slash-engineering ever attempted.

Built with Purpose

This wasn’t some hackjob garage swap. Volkswagen reportedly spent €2 million developing the prototype. The W10 itself was essentially two VR5 engines fused together, but unlike traditional VR units, this one featured a lightweight aluminum block. VW even fabricated a bespoke carbon fiber airbox and ran the engine through a standalone ECU.

Inside, it’s a different world. The car’s been stripped of driving aids—no ABS, no traction control, no stability system. It has auxiliary gauges and a race-inspired instrument cluster. It smells of fuel and raw exhaust. It’s as raw as any prototype comes.

And rumor has it, Ferdinand Piëch drove it to work. Daily.

Three Engines, One Car

Volkswagen reportedly built three W10s. The one featured in the DriveTribe video lives inside the M5. The second engine, once thought to be lost, surfaced in Germany in 2023 with a VW mechanic who was told the others had been destroyed. The third? It’s now believed to sit in a private collection—still intact, still mysterious.

This isn’t the first M5 with a crazy engine from another brand. One of Bavaria’s best-kept secrets is using an M5 E34 Touring as a test mule for the V12 that went into the McLaren F1. Sadly, the M division has refused to show the super wagon in public. Hopefully, BMW Classic will reveal the ultimate E34 one day, unless they’ve scrapped what would’ve been the one family car to rule them all. We like to believe it hides deep in BMW’s warehouse.

For Sale—If You Dare

The W10 M5 is now up for grabs. The asking price? Around $500,000, roughly the same as a Ferrari Purosangue. It’s an insane number, sure—but then again, when you’re buying a one-off prototype built by VW’s top engineers, handpicked by Piëch himself, you’re not just buying a car. You’re buying a story.

[Source: Drivetribe]