2025 Mercedes-Benz G 550 Tested: Smaller Engine Brings Performance Gains

• The 2025 Mercedes-Benz G 550 ditches its V8 in favor of a new inline-six.
• Our performance testing shows improvements in acceleration and quarter-mile times compared to the outgoing G.
• The new G 550 also does better in our hard braking test.

The turbocharged 3.0-liter inline-six powering the G 550 is a potent one. It puts out 443 horsepower and 413 lb-ft of torque, which represents an increase of 27 hp and a decrease of 37 lb-ft compared to the old V8. There's also a standard 48-volt integrated starter-generator on hand to provide as much as 20 hp and 148 lb-ft of supplemental boost to get the G-wagen up and moving, and to smooth out the operation of the engine's stop-start system. The G 550 available exclusively with four-wheel drive — plus a proper low range and locking differentials for mega off-road prowess — and a nine-speed automatic transmission.

Before getting on the track, we weighed the G 550 as we do with every test vehicle. The 2025 model checked in at 5,689 pounds with a full tank of gas. That's heavier than the previous G 550 we tested, but only by about 20 pounds.

On the straightaway, the G 550 sprinted from 0 to 60 mph in 5.1 seconds, beating Mercedes' own estimate by 0.2 second. It then continued on to complete the quarter mile in 13.7 seconds at 98.3 mph. For context, a 2019 G 550 with a V8 hit 60 mph in 5.6 seconds and ran the quarter mile in 14.0 at 98.3 mph. So the new model is 0.5 second quicker to 60 mph and 0.3 second quicker in the quarter mile despite having a smaller engine.

For even more context, the 2024 Lexus GX took 6.7 seconds to reach 60 mph and 14.9 seconds to finish the quarter mile. A six-cylinder Land Rover Defender 110 matched the Lexus' numbers in our testing, also making it significantly slower than the G 550.

It's not just acceleration where the new G 550 improves either; we saw massive gains in the 60-0 mph braking test as well. The G 550 stopped from 60 mph in 108 feet — an enormous 27-foot upgrade over the previous model's 135 feet. To put it another way, the new G 550's braking performance matches that of a Honda Civic Type R on our test track. That 108-feet readout is leaps and bounds ahead of the competition, too: The GX did 128 feet, and the Defender did 133 feet. In the real world, that could make a huge difference in an emergency-stopping situation.

We normally subject our test vehicles to a 200-foot lateral-g skidpad, but it was under construction at the time of testing. Around our handling circuit, the G 550 felt familiar to its predecessor, but there was one big difference. For as much as we applaud the gains in performance, the inline-six is a major letdown in the noise department. Without the signature grumble from the V8 that we've come to adore in the G-wagen, things just don't feel right. But considering Mercedes sells more G 63s than G 550s anyway, perhaps this'll just continue to skew things in that direction.