AMG has been caught testing the E53 in Europe on multiple occasions, but this is the first time we're seeing the sports saloon on US soil. Spotted with full camo attire in California, the Audi S6 rival had unusually long exhaust tips that certainly won't look like that on the production model. Attached are spy shots of different prototypes with the usual quad tips. This US-spec vehicle was likely being tweaked to meet local emissions regulations.

Aside from the obvious design changes compared to the previous-generation AMG E53, there is a major change hiding in plain sight. The rear fender on the driver's side has a cap for the charging port, which can only mean the prototype is boasting a plug-in hybrid setup. The C63 S E Performance and the S63 E Performance are also of the PHEV variety and have the charging port in the same location.

2025 Mercedes-AMG E53 Sedan and E53 Wagon spy photos

While the C43 and C63 have been demoted to a four-cylinder engine while the S63 has kept the V8, the new E53 and E63 are expected to split the difference by offering a six-cylinder unit. It's likely the 3.0-litre inline-six working with an electric motor, possibly making a little over 500 bhp in the E53 to mirror the Benz- and Maybach-branded S580e. In those electrified fullsize saloons, the ICE is good for 367 bhp and 368 lb-ft while the e-motor delivers another 150 bhp and 324 lb-ft. Together, the combined output stands at 510 bhp and 553 lb-ft. 

We wouldn't get our hopes up too high for the more practical estate to make it stateside as MB USA only sells the full-fat E63 Estate. As for those dreaming about the return of the V8 in the range-topping model, AMG CEO Michael Schiebe recently said it's not going to happen, despite the rumours claiming otherwise. The future E63 is likely to be a plug-in hybrid based around an inline-six as well, presumably with more oomph than the 671-bhp C63 S E Performance.

It's worth noting a future BMW competitor for the next-gen AMG E53 will also be a plug-in hybrid. It hasn't been announced yet but insiders are claiming the new 5 Series in M Performance guise is due in 2024 as an M560e with an electrified six-cylinder powertrain. Even the mighty M5 will be a PHEV, but unlike the AMG E63, it's going to keep the brawny V8.