The world's first mass-produced diesel hybrid - that is, a car using a diesel engine backed up by an electric motor - was the Peugeot 3008 HYbrid4, launched in 2012. The 3008 diesel hybrid offers the fuel-efficient benefits of diesel and electric technology in one eco-friendly package, and is therefore much more economical than an equivalent petrol-only vehicle. However, Peugeot is not the only company with a diesel hybrid up its sleeve - Mercedes-Benz is also readying a model of its own, the E 300 BlueTEC Hybrid, with a view to incorporating this technology into other vehicles in future. Peugeot, meanwhile, plans to install its HYbrid4 technology in its upcoming 508 RXH.
But, for now, let's focus on the companies' first diesel hybrid models. We'll look at several aspects of each vehicle, comparing as we go:
The 3008 HYbrid4 is unusual not only because it features a diesel engine and an electric motor, but because there is no physical link between the front diesel-powered axle and the back electric-powered axle. Everything is computer controlled - the onboard electronics work out the most efficient way to use each power source. This is a simple and effective way of reducing emissions which also means that the diesel hybrid technology can easily be adapted to fit any car in Peugeot's range. Mercedes-Benz also opts for a modular diesel hybrid design.
Both cars use a four-cylinder diesel engine - Peugeot's boasts a power output of 120 kilowatts whereas the Mercedes-Benz has a slightly higher output of 150 kilowatts. However, the Peugeot has a more powerful electric engine, rated at 27 kilowatts, compared to the 300 BlueTEC's 20 kilowatts. In terms of torque, the cars are equally matched - the 3008 and the 300 BlueTEC both deliver up to 500 newton metres of torque.
Peugeot's diesel hybrid has a secret weapon when it comes to performance, however - and the clue is in the name 'HYbrid4'. Using a simple control, its driver can choose between four 'driving modes' which control how the diesel hybrid makes use of its power sources. These are:
Auto: Puts the car in control of the entire system, transitioning between the power sources as necessarily. This achieves the optimum balance of fuel efficiency and driveability.
ZEV: In 'Zero-Emission Vehicle' mode, the car uses the electric motor as its sole power source, meaning no harmful emissions are produced. Great for short-distance city hops.
4WD: In this mode, each power source is used as often as possible - because the front wheels are driven by an engine and the rear wheels are driven by the electric motor, this results in four-wheel drive.
Sport: Allows for quicker gear changes at higher speeds.
Whilst Mercedes-Benz's diesel hybrid can be driven in all-electric mode, it lacks the versatility of Peugeot's model. Peugeot's diesel hybrid can also be driven in electric mode for longer - with a range of up to three miles when driven at speeds below 35 miles per hour. The Mercedes-Benz, on the other hand, can manage just over half a mile when driven at speeds up to 22 miles per hour.
Peugeot and Mercedes-Benz have both launched innovative diesel hybrid cars. This guide looks at the best aspects of the Peugeot 3008 HYbrid4 and the Mercedes-Benz 300 BlueTEC Hybrid.