This news might sound like deja vu. Mercedes-Benz Vision EQXX, the brand’s globe-trotting technology demonstrator doing all the hard work so that future road-going Mercedes EVs can be as efficient as possible, just covered 627 miles on a single charge. Yes, again. But this time its energy efficiency was even better.

Mercedes engineers drove the Vision EQXX longtail across the Arabian desert. The EV traveled from Riyadh, Saudi Arabia, to Dubai, UAE. It clocked an efficiency of 8.4 miles per kilowatt-hour, as its aerodynamic form factor cut through the air, battled desert heat, and covered hundreds of miles on battery power across empty highways.

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Mercedes-Benz has taken a step back from EVs, but R&D continues.

Mercedes-Benz had committed to an all-electric portfolio by 2030. But with the recent EV sales slowdown worldwide, and an impending presidential election in the U.S. which could shape the EV industry going forward, the German automaker has taken a step back. But that doesn’t mean it’s sitting idle. A new EV based on the one-size-fits-all MMA platform will debut later this year, and development for future EVs is underway as well.

In its first outing from Sindelfingen, Germany to Cassis, France, the EQXX covered an equally impressive 626 miles but the efficiency was comparatively lower at 7.1 miles/kWh. That was in 2022. Again later the same year, the EQXX road tripped from Stuggart to Silverstone, covering 747 miles on a single charge, averaging 7.5 miles/kWh.

A 2023 Tesla Model 3 Long Range AWD has an efficiency of about 3.8 miles/kWh, according to the EPA. Even though the Tesla is aerodynamic in its own right, it doesn’t have any of the additional aero chops of the EQXX. The Mercedes is extremely slippery, with a drag coefficient of 0.17, better than any production sedan.

It also gets a streamlined rear section with an additional aero blade under the rear bumper stretching out and away from the body to make the air exit from the undercarriage as smoothly as possible. It’s also made from materials you normally don’t see in affordable mass-market production cars, like weight-saving carbon fiber reinforced plastic.

So it’s unclear how much of this efficiency we’ll ever see in the real world. That said, it averaged 42.7 miles per hour, delivering 282 MPGe. The air conditioning was on along the way, and a “multi-source heat pump” minimized energy losses, Mercedes said. The EQXX has a 100 kWh battery capacity based on a 900-volt system architecture.

“The EQXX continues to provide valuable data for developing advanced electric efficiency technologies. All systems performed perfectly in the desert, handling challenges such as road surface finish, temperatures, and dust, with ease,” Markus Schäfer, the chief technology officer at Mercedes-Benz AG, said. “It’s proof that electric drive is ready for global markets.”

Mercedes-Benz also said the EQXX is a close-to-production concept, previewing the model family based on its next-generation MMA platform. Some of its heat pump tech is carried over to the Concept CLA that Mercedes showcased in 2023. The MMA will spawn into the next generation CLA, in addition to two crossovers and a station wagon.