This E39 BMW M5 Hides a Long-Lost Volkswagen W10 Engine

In 2023, we published a story about what many believed to be the last remaining W10 engine built by Volkswagen in the early 2000s. It was in the hands of a German VW mechanic who was told that the other two engines made were destroyed. Fast-forward to 2025, and we finally know where to find them. Both are part of a private collection, and one is stuffed in an E39-generation BMW M5-based test mule.

The W10 project was the brainchild of Ferdinand Piëch, who was the chairman of the Volkswagen Group until 2015. The W range of engines, which included the W8 that ended up in the Passat 4Motion, the W12 found in several Volkswagen, Audi, and Bentley models, and the W16 that powered the Bugatti Veyron, was developed under his watch. Two additional W engines were developed but never mass-produced: The W10, which was reportedly envisioned for a sport sedan, and the W18, which the Veyron was supposed to use until engineers chose a W16.

Official details about the W10-powered sport sedan are lost to history, but a recent Drive Tribe video claims there was nothing like it in the Volkswagen Group’s portfolio. This complicated the task of putting the engine through its paces in real-world conditions, so Volkswagen purchased an E39-gen M5 to use as a test mule. Piëch’s team chose the M5 for several reasons. One is that there was enough space in the engine bay to mount the W10, which was a lot more compact than a V10 due to its W layout. Another is that the M5 was developed to offer excellent handling, so there was no need to make major changes to the chassis. And, the subtle styling certainly helped; To the untrained eye, the E39-generation M5 looks pretty much like a run-of-the-mill 5 Series sedan. The six-speed stick was another determining factor.

Volkswagen reportedly spent about €2 million building the one-off, W10-powered M5, and one look under the hood tells you exactly where the money went. This is a dauntingly experimental build, yet the workmanship is immaculate. There are no loose or hanging wires, no random parts cobbled together with tape, and nothing that looks unfinished. Volkswagen even built a carbon fiber airbox for the engine.

It’s still a prototype, however. It’s not fitted with any kind of driving aids as VW even left out ABS and traction control. The instrument cluster looks like it’s from a race car, there are several auxiliary gauges on the center stack, and engineers rigged up a standalone ECU to run the drivetrain. Fuel and exhaust fumes permeate the cabin, but that didn’t stop Piëch from reportedly driving the M5 daily for a while.

He probably had a blast!

Linked to a six-speed manual, the W10 makes 480 horsepower and 436 lb-ft of torque at the wheels. For context, a stock E39-gen M5 uses a 4.9-liter V8 that produces 394 hp and 369 lb-ft of torque at the crank. Sure, the W10 is likely heavier, but that’s still a nice bump in power. It sounds amazing, too. It’s too bad that this engine never saw the light that awaits at the end of a production line.

The one-of-a-kind, W10-powered M5 is for sale, and it costs approximately as much as a new Ferrari Purosangue, according to Drive Tribe. We’re guessing it’ll take about $500,000 to add it to your collection. Is it worth it? It depends on your perspective, and there’s no right or wrong answer, but we’d argue that half a million dollars doesn’t sound entirely unreasonable given the prototype’s rarity and coolness.

Now, we’re curious: Are there other W10s out there? And what happened to the one we wrote about in 2023?

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