Mercedes-Benz S500 Plug-In Hybrid review

The Mercedes S-Class has always been the luxury car benchmark. Can it also be an economy car yardstick too? Sounds crazy but it might just be possible. Jonathan Crouch reports.

Ten Second Review

The Mercedes-Benz S500 Plug-In Hybrid promises economy figures as high as 100.9mpg. While this sounds wildly optimistic, stick with this. There's some seriously clever technology at work here.


You don't really need to come up with elaborate justifications to buy a Mercedes-Benz S-Class. It's the best car in the world. Buying anything else is making do, no? Well just in case you thought that even the petrol/electric hybrid S400 model and the diesel/electric S300 BlueTEC Hybrid models were somewhat excessive - and at 64.2mpg for the former, that's a hard charge to make stick - Mercedes have something that may well pique your interest. A Mercedes S500 wouldn't at first seem like the obvious answer. With a turbocharged 3.0-litre engine and a total power output of 442bhp, this sounds like a bit of an old-school hot rod. In fact it's anything but and to give the car its full title explains why. The S500 Plug-In Hybrid is a work of engineering genius. A powerful limousine that can get better than 100mpg? It sounds bizarre, but it's now a reality.

Driving Experience

Mercedes is making up for lost time when it comes to hybrid technology. The petrol/electric S400 is a template for what most people expect of a hybrid car. The diesel/electric S300 is a little bit further out there, but if you're the sort of early adopter who has their gear on eBay by the time it picks up its first reviews, the S500 Plug-In Hybrid might well be old news. For the rest of us, it's something bafflingly otherworldly. It's powered by a 333bhp 3.0-litre V6 turbocharged engine which is bolstered by the addition of a 116bhp electric motor. The combination of the two generates a total of 442bhp and 650Nm of torque. Like the rest of the S-Class range, this car has a limited top speed of 155mph. It'll travel up to 20 miles on electric power alone and the driver can select between four different driving modes: 'normal hybrid', 'electric power only', 'electric power save' and 'charge'. To help maintain efficiency, Mercedes has developed what it calls a haptic accelerator. This means that there's a dynamic resistance point built into the throttle's travel to alert when the petrol engine is set to cut back in, allowing the driver to nudge up to that limit on battery power alone. Ignore all that, drive it as if you've stolen it and you'll demolish 62mph in just 5.2 seconds.

Design and Build

Fortunately, Mercedes hasn't fitted the S500 Plug-In Hybrid with any weird aerodynamic body styling. To all intents and purposes, it looks like any other S-Class - which is a good thing. Pop the fuel cap and you'll also find a seven-pin electrical socket but other than that, it's wholly conventional. Of all things, the lighting system deserves more than a passing mention. More than 100 years after the introduction of electric lighting in motor vehicles, Mercedes-Benz is making a complete switch to LED technology - this S-Class is the first vehicle in the world whose interior and exterior do without a single light bulb. Out of consideration for any road users behind, the intensity of the brake lights is reduced at night or while waiting at traffic lights, which is no bad thing. Some Mercedes models in the recent past have had antisocially bright tail lights. Mind you, this one is certainly going to be well lit up after dusk. Almost 500 LEDs illuminate the road, the vehicle, the interior and the boot. Depending on equipment, these include headlamps with up to 56 LEDs, tail lights each with up to 35 LEDs (plus 4 for the rear fog lamp) and no fewer than 300 LEDs in the interior, including the ambient lighting. The car wears its size with a light touch and there's plenty of room inside the beautifully-finished cabin. You can even specify the "First Class Rear" where the front console on the transmission tunnel is visually continued to the rear. It's equipped with innovative thermo-cup holders which use Peltier technology to cool or warm drinks over a longer period of time. Like an aircraft seat, the centre console is available with two tables which can be folded in or out using one hand. You will have to make do with a vastly reduced boot volume in order to accommodate the battery pack though, but sacrifices have to come from somewhere in the name of efficiency.

Market and Model

The S500 Plug-In Hybrid requires a budget of around £90,000. The car comes only in long wheelbase form and equipment is based on the AMG Line spec. This includes 19-inch alloy wheels, AMG body styling, the LED Intelligent Light System, the COMMAND Online infotainment system, noise insulating glass, leather upholstery and a front seat memory package. As for other features, Mercedes has made some big strides in terms of safety equipment which, bundled together, it refers to as Intelligent Drive. Using a stereo camera and multistage radar sensors, the S-Class marshals the adaptive cruise control, lane guidance and Brake Assist System BAS PLUS with Cross-Traffic Assist, which is able to detect crossing traffic and pedestrians, boosting the braking power applied by the driver accordingly. In the back, there are belt bags; inflatable seat-belt straps that are able to reduce the risk of injury to passengers in the rear in a head-on collision by lessening the strain placed on the ribcage. The reclining seat is equipped with a cushion bag under the seat cushion upholstery as standard. When the seat is reclined, it prevents the occupant from sliding beneath the seat belt (so-called submarining) in an accident.

Cost of Ownership

That headline 100.9mpg fuel economy figure sounds freakish. How's it achieved? A whole variety of methods, actually. The plug-in aspect of this car means that you can pre-charge the batteries before heading out - and these aren't like the batteries you'll find in a Prius. In fact, these lithium-ion batteries have ten times the energy content compared to the unit in the existing S400 and S300 Bluetec Hybrids, so you're really bringing the juice here. My favourite bit is Mercedes' brilliant anticipatory energy management system. This examines your driving style and constantly adjusts how the hybrid system recharges its batteries to suit. The really smart bit is that if you're driving a route on sat nav, it'll analyse the next five miles of the journey and anticipate hills, speed limits and corners, making the most of the electric motor's torque where necessary and switching quickly into energy regeneration mode where it can. Emissions are rated at 69g/km which is pretty nominal, depending on how long the car's running on electric power. It'll even manage to put a lick on Toyota Prius hybrid in terms of both economy and emissions. Clearly there will be a price to be paid for this ground breaking technology but as a showcase for the engineering muscle of Mercedes-Benz, the S500 Plug-In Hybrid is utterly remarkable.


The Mercedes-Benz S500 Plug-In Hybrid takes your perceptions of what a big car ought to be capable of and tramples them to smithereens. Conventional wisdom dictates that you just don't get limousines that will outsprint a Porsche yet be more economical than a Prius. To suggest so would hint at some sort of automotive alchemy. Yet that's exactly what Mercedes has achieved with this S-Class. This two-tonne car will sprint to 62 mph in just 5.2 seconds, yet its combined fuel economy figure is 100.9mpg and it emits 65g/km of carbon dioxide. How relevant is all this to those of us who can't afford an S-Class though? You might well be surprised. The trickle-down of technology from luxury flagship models to more proletarian pricing happens so much quicker these days. If Mercedes can do this with an S-Class, they can do it with an A-Class. Making it cost-effective to a value-conscious customer base might be a tough ask, but a few years ago we'd have figured the numbers this car makes were utterly impossible. The future? It just arrived.