The lack of any diesel versions of the current E-class in the United States is cause for sadness and regret in some quarters, but we can understand Mercedes-Benz’s reluctance to bring them here given the awkwardness of that whole Dieselgate thing. Yet the decision not to import the plug-in-hybrid version of the E is more surprising, especially since it has been on sale in Europe for more than a year and uses a version of the turbocharged inline-four gasoline engine found in the base E300 combined with a generous dose of electrical assistance.
Yet there’s logic here, too—it’s not as if U.S. buyers showed much enthusiasm for the previous-generation E400 hybrid, or even the smaller C350e plug-in hybrid that shares most of the E-class version’s powertrain and is currently sold here. Mercedes is on the record as saying it plans to bring a hybrid E-class to North America by the end of the decade, but there seems to be no sense of urgency. Having grown bored of the wait, we sourced a representative example in the United Kingdom to gauge how resentful we should feel about being denied it.
What Is It?
The E350e’s powertrain combines the efforts of a 208-hp turbocharged inline-four with an 87-hp electric motor situated between the engine and the nine-speed automatic gearbox (the C350e uses the older seven-speed unit). This is fed electrons flowing from a 6.2-kWh battery pack mounted beneath the trunk floor, giving a claimed total system output of 282 horsepower. The battery can be recharged through a port on the rear bumper, with Mercedes quoting three hours to charge it from a European 220-volt outlet or half that with a DC fast charger; alternatively, it can be replenished by the engine.
Mercedes claims a 21-mile electric-only range, although this is measured using the notoriously optimistic European test methodology. All the same, the electric assistance can dramatically reduce fuel consumption on short-haul trips. The system is smart, too, working out the most efficient strategy when a destination is programmed into the nav system, running the battery down if it knows it will end up at a regular charge point or trying to maintain battery level if heading toward an urban area.
The system also can be given commands. The default Hybrid mode leaves it to its own devices, but there’s also E-Mode, which turns the E350 into an EV until the battery is depleted; E-Save, which maintains the charge level for later use; and Charge, which uses the gasoline engine to replenish the battery pack on the fly.
As is often the case with luxurious hybrids, initial impressions are good. At the gentle speeds we first experienced in the E350e, the electric motor proves to be smooth and almost silent, pulling seamlessly and—in Hybrid mode—permitting respectable pace before the gasoline engine fires to life. Freezing temperatures when we drove the car limited electric range more than usual, so the battery pack was emptied from full in just 12 miles of E-Mode operation, but it isn’t intended to be an EV very often. The accelerator pedal incorporates a neat haptic function under electric use, putting resistance at the point where the motor is giving its all; press beyond that and the internal-combustion engine starts, giving near-instant acceleration if you find a sudden need for it.
Under acceleration the two sides of the powertrain work together almost flawlessly, but stopping is slightly less composed since at lower speeds the regenerative braking gives way to the mechanical brakes at a quicker rate than the system blends in old-fashioned friction braking. It’s surprisingly hard to achieve a chauffeur-smooth halt, normally something at which Mercedes sedans excel.
It’s when the E350e is asked to deliver faster progress that it starts to struggle. It’s the familiar hybrid problem: The need to carry the mass of two different propulsion systems means that it doesn’t feel as quick as its total system output suggests it should. Its maker’s claim of a 6.2-second zero-to-62-mph time feels right, and the E certainly leaves the line with a satisfying snap in a full-throttle-stomp scenario. But as speed rises, the contribution made by the electric side of the powertrain begins to diminish while the considerable mass of the battery pack and the motor remain the same. Once at a rapid highway pace—or a British simulation thereof—it subjectively feels no faster than does the E300; the four-cylinder engine also gets pretty vocal under harder use. It doesn’t feel as quick or refined as a Mercedes wearing a 350 badge should.
As with most hybrids, the fuel economy depends entirely on the sort of journeys the car is used for. An E350e that just hops between inner-city charging points might rarely start its engine, but one that is used predominantly for longer trips will see almost no mileage benefit compared with the E300. We didn’t run a proper fuel-economy test, but the trip computer reported the U.S. equivalent of 37 mpg after a 30-mile journey that also included using the entire battery charge. That limits its appeal in Europe, where diesels remain more frugal for anything except the shortest of journeys; gasoline will have to be a whole lot more expensive before it makes much sense in the U.S., either. We don’t like to be denied cars, but we can see the logic of Mercedes on this one.