[GregW / Oregon]

Here's a description of the initial V8 offering for the GLS:

"Shortly after the model series launch, the introduction of the GLS 580 4MATIC (combined fuel consumption: 10.0-9.8 l/100 km; combined CO2 emissions: 229-224 g/km) will mark the world premiere of a new, electrified V8 petrol engine with 48-volt on-board electrical system and integrated starter-generator. It has an output of 360 kW (489 hp) and 700 Nm of torque, with a further 250 Nm of torque and 16 kW/22 hp available via EQ Boost over short periods. The integrated starter-generator (ISG) is responsible for hybrid functions such as EQ Boost or energy recuperation, while allowing fuel savings that were previously reserved for high-voltage hybrid technology.

ISG eliminates the need for a belt drive for ancillary components at the front of the engine, which reduces its overall length. The slim design of the engine, together with the physical separation of intake/exhaust, creates space for close-coupled exhaust aftertreatment. The 48 V on-board electrical system serves not only high power consumers, such as the water pump and air-conditioning compressor, but also the integrated starter-generator (ISG), which also supplies energy to the battery by means of highly efficient energy recuperation."

The six-cylinder version of this technology has gotten excellent reviews.