MERCEDES BENZ HYBRID CAR

tHE FACT SHOW THE PERFORMANCE OF HYBRID CARS AFTER TEST DRIVE

2015 Mercedes-benz s550E plug-in hybrid

INSTRUMENTED TEST

Between instrumented tests and first drives, we’ve published 12 reviMews of the latest-generation Mercedes-Benz S-class in the past two years, spanning the bread-and-butter S550 to the opulent S600 Maybach and over to the sinister S65 AMG coupe. Let’s take that to lucky number 13. Enter the S550e, a plug-in hybrid for those who think the Cadillac ELR is a joke and the plug-in Panamera a bit too, well, Porsche. The added electro-tech is a no-cost option: A 2015 S550e will run you $95,325—exactly the same money as the V-8 car.

If we’ve reviewed a car 13 times in the space of two years, there is one of two things going on: 1) We find the vehicle continually newsworthy, or 2) you readers click the high holy heck out of S-class stories. There’s undoubtedly some overlap there. Plus, with all of the amenities thrown into the current-generation S-class, can you begrudge a heap of stooped scribes their turn at the tiller of what is unquestionably one of earth’s great vehicles? Having read instalments one through ten (you have, haven’t you?), you know that the S-class will offer you a hot stone massage, perfume the air, magically control both its body and the sky, largely drive itself, and generally treat you like the lord of a 206.5-inch-by-74.8-inch fiefdom.

So the story here is one largely of numbers. Let’s start with 18 miles. That’s the distance from the historic gold-mining town of Auburn, California to Foothill Farms, a census-designated place outside Sacramento. That’s also the distance the S-class carried us at 70 mph, using solely electric power, while steering itself. Our only intervention was to touch the steering wheel every 10 to 15 seconds to make sure the large sedan continued its autonomous, electrified undertaking. We should, however, qualify that accomplishment by noting that those 18 miles saw roughly a 1000-foot drop in elevation. As always, your mileage may vary, but if you have a 10-mile commute to work and a plug at the office, the S550e’s 8.7-kWh battery pack could put you, the VP of finance, on a carbon-footprint par with those quinoa-snorting Tesla drivers over in engineering.

With its turbocharged six-cylinder plus electric motor, the S550e is not exactly a Model S P85D. Still, a 13.6-second quarter-mile at 103 mph puts the plug-in only 0.2 second behind its lighter, twin-turbo V-8–powered sibling. On the drag strip, we found that the abrupt hit of power from the electric motor made it hard to launch, although it was a tad quicker than the off the line and recorded an identical 60-mph sprint of 4.9 seconds. In our lateral-acceleration testing, the plug-in suffered mightily against the V-8 car, posting a mere 0.81 g to the regular 550’s 0.87. Sure, the 482-pound weight penalty hurts, but we’d lay blame at the feet of the Michelin Primacy MXM4 all-season tires. Compared with the Goodyear Eagle F1 Asymmetric 2 summer rubber on the S550 we tested, the hybrid gives up a big chunk of grip.

Which brings us to the one major luxury bugaboo with this S-class hybrid. Picture yourself in the Savile Row suit of a London banker who works in the city’s congestion zone. As a man of means, you’ve purchased an S550e to be chauffeured to work in, while neatly avoiding the onerous fossil-fuel fees imposed upon you by city officials, thanks to the car’s ability to run solely on electric power. But every time your man Stanislav attempts to modulate the brakes to bring the car to a jerk-free stop, he fails.

You know the old boy’s got it in him. When you picked up your Phantom, you had Stan trained by Rolls-Royce’s White Glove specialists. He does a bang-up job in the Range Rover; not so much of a speck of jam or clotted cream has fallen on your jodhpurs during jaunts to the country place. But this Benz hybrid’s regenerative braking system simply won’t allow it. Certainly, during a spirited romp on a rural lane, they work nicely, but you’ve got Dad’s old XK140 for those sorts of days out. This ghastly old brake business! It’s enough to make a chap contemplate paying the congestion charge!

And unless you’re assiduously plugging in or saving mountains of cash on parking or congestion fees, the hybrid S simply doesn’t make much sense over the V-8 car. The last S550 we tested came in at 20 mpg. This S550e Plug-In? 20 mpg. The car’s EPA numbers suggest 24/30 mpg city/highway, while the nonhybrid S550 posts 17/26. We drove the S550e as if it were a normal car. The full charge we used for our 18-mile freeway cruise came courtesy of charging the battery via the car’s engine, which is a wasteful way of doing things. If you’re religious about plugging in, your numbers could be drastically different (note the car’s 58 MPGe rating from the EPA, which surpasses the plug-in Panamera’s 50 MPGe score while coming far short of the ELR’s 82 MPGe). But if you’re considering an S-class for everyday duty, might we steer you toward the quicker, lighter, and—under our feet, at least—just-as-efficient V-8 model?