First is the 2015 Mercedes-Benz ML400 4Matic, which replaces the outgoing ML550. The ML550 had a 402-hp V-8 engine displacing 4.7-liters, but it sucked down fuel with reckless abandon, achieving efficiency ratings of 14/19/16 mpg (city/highway/combined). The 2015 Mercedes-Benz ML400 4Matic uses an aluminum-block 3.0-liter twin-turbo V-6 making 329 hp and 354 lb-ft of torque, which returns 18/22/20 mpg (city/highway/combined). A seven-speed automatic transmission comes standard, as does an engine stop-start feature. Yes, that's less power than the V-8, but the fuel-economy bump is more than welcome.

2014 Mercedes Benz ML350 BlueTEC 4MATIC side view field

Hoping to position the 2015 Mercedes-Benz ML400 4Matic as a well-equipped and more-efficient alternative to the older V-8, the German automaker is also including standard leather upholstery, keyless entry, lane-keep assist, Harmon/Kardon premium audio, multi-color ambient lighting with heated and cooled front cupholders, as well as an AMG appearance package which features 19-inch AMG wheels.

The other new powertrain fits in the 2015 Mercedes-Benz ML250 BlueTec, which replaces the ML350 BlueTec. This diesel-powered SUV adopts a 2.1-liter twin-turbo inline-four engine making 200 hp and 369 lb-ft of torque — already available in the Mercedes-Benz E-Class and GLK-Class. Like the aforementioned ML400, the ML250 also adds stop-start as standard. Although it's not as powerful as the old ML350 Bluetec's 240-hp V-6, which made 455 lb-ft of torque, the new engine's smaller size means that the 2015 ML250 BlueTec weighs almost 300 pounds less than before. Official EPA fuel economy ratings are as yet unavailable, but the outgoing ML350 BlueTec (pictured) was rated for 20/28/23 mpg (city/highway/combined). We expect the ML250 Bluetec to hit the 30-mpg highway mark.

Two other versions of the 2015 Mercedes-Benz ML stay the same. The ML350 continues with its 302-hp, 3.5-liter V-6 engine, and a choice between rear-wheel-drive or 4Matic all-wheel drive. The ML63 AMG packs a 518-hp punch from its twin-turbo 5.5-liter V-8 engine.

The 2015 Mercedes-Benz ML400 will start at $63,825 including destination fees, although prices for other models have yet to be announced. The 2015 Mercedes-Benz ML350 hits showrooms this month, the ML400 goes on sale toward the end of August, the ML250 BlueTec goes on sale in early September, and the ML63 AMG coming in late September.