Though nearly everything about them is new, the essence of the E-Class cars hasn't changed.They retain the feeling of robustness and engineering excellence that has defined them for decades.

The E-Class sits in the middle of the Mercedes car line, between the compact C-Class and the big S-Class.Though it's no longer Mercedes' biggest seller in the United States, the E-Class remains the company's best-selling car worldwide, and as such it defines the brand's essence.Every E-Class model delivers an excellent balance of passenger space, luxury, style and impressive performance in a practical, manageably sized package.

The E-Class line has been expanded, with a two-door Coupe joining the familiar sedan.Wagon and convertible variants will be available across the United States by late spring 2010.The new E-Class looks more angular, perhaps more technical, than its predecessors, but it is quite pleasing to the eye.The underlying structure of all variants has been strengthened to improve crash protection, reduce vibration and sharpen handling, without adding weight.Yet if the new-generation E-Class cars have a theme, it might be their high-tech control and management systems.That's not surprising for a car that introduced a host of now-familiar features, from antilock brakes to airbags, to mass production.

The 2010 Mercedes-Benz E-Class represents the most electronics-intensive model line Mercedes has offered to date, and most of the new computer-managed systems focus on safety.A new Attention Assist system that comes standard monitors up to 70 driving parameters to determine whether the driver is getting drowsy behind the wheel and uses both visual and auditory warnings to tell the driver to pull over for rest.The Distronic Plus cruise control option features both blind-spot warning and lane-departure warning technology, while automatic self-adjusting headlights automatically dim the brights.And those systems are just the start.

Beyond the technological wizardry, the E-Class remains what is has always been, only maybe a little bit nicer.Every model is smooth, quiet and appointed in elegant, understated fashion, with comfortable space for four or five passengers and a substantial load of luggage.

The new sedans are very attractive and the new two-door Coupe might be the sexiest E-Class car ever.

The standard gasoline V6 in the Mercedes E350 models is more than powerful enough for most drivers.The 382-horsepower V8 in the Mercedes E550 models delivers the turbine-like, overpowered feel that characterizes Germany's best autobahn blasters.The turbocharged engine in the Mercedes E350 BlueTEC sedan is the smoothest, quietest diesel available in the United States.It delivers amazing bursts of acceleration for passing, with mileage that surpasses most other cars in this class by about 30 percent.Those seeking help through the worst of a northern winter can choose the 4MATIC all-wheel-drive system for the E-Class sedans and wagon.

The E-Class created a category of mid-sized luxury cars that has become one of the most competitive (and enjoyable) in today's automobile market.The 2010 E-Class models simply re-establish Mercedes credentials near the top of the class.

The E350 sedan ($48,600) comes with automatic dual-zone climate control, burl walnut trim, 14-way power front seats with position memory, an eight-speaker stereo with six-CD changer and Bluetooth interface, and 17-inch alloy wheels.The standard upholstery is cloth.The E350 BlueTEC sedan ($49,600) is equipped similarly.The E550 sedan ($56,300) comes standard with leather upholstery and a power sunroof.

4MATIC all-wheel drive ($2,500) is optional.

The 2011 E350 4Matic wagon (June 2010) comes only with all-wheel drive and the 3.5-liter gasoline V6.

The E350 Coupe ($48,050) and E550 Coupe are equipped comparably to the sedans.

The 2011 E350 Cabriolet and E550 Cabriolet (May 2010) resemble the two-door Coupe but feature a power-operated fabric convertible top and a number of features intended to allow open motoring year-round.

The E63 AMG sedan ($88,625) features a 6.2-liter V8 that generates 518 horsepower and 465 pound-feet of torque.It adds a host of performance upgrades, including a seven-speed transmission with an automatic clutch rather than a conventional torque converter.

Options are clustered in two groupings.Premium Package I ($3,950-$4,400, depending on the model) adds a navigation system, premium harman/kardon audio with HD radio and Sirius satellite radio hardware, heated front seats, a back-up camera and rear-glass sunshade.Premium Package II ($6,350-$6,800) includes Package I plus ventilated front seats, a bi-xenon active light system with automatic high-beam control and headlight washers, and keyless entry.Standalone options include rear-seat DVD entertainment ($1,850), Panoramic Sunroof ($1,590), split folding rear seat ($430).

Safety features include advanced antilock brakes (ABS) and electronic stability program (ESP).Active safety systems include Attention Assist drowsiness monitor.Standard passive safety features include nine airbags: dual frontal, driver's knee-protection, front-passenger side-impact torso, front passenger side-impact pelvis, and full cabin head-protection curtains.Rear passenger side-impact airbags are optional.

With the redesign, Mercedes has also re-aligned the E-Class nomenclature.Besides the familiar sedan and wagon, the line-up once again includes an E-Class Coupe and Cabriolet (or convertible), which replace cars that had been known as the CLK since the mid-1990s.All E-Class models share the same underpinnings, and nearly identical exterior dimensions.

Styling for all E-Class variants is quite similar, too, at least from the windshield forward.Every design cue, panel, lamp and piece of glass has been changed compared to the outgoing models.And although they tend to look bigger than their predecessors, more like Mercedes' premium S-Class, they really aren't.The new E-Class variants share a larger grille, and a new trapezoidal headlamp array with multiple elements and square corners instead of the traditional E-Class oval lamps.

From the windshield back, the new E-Class models differ, of course.The two-door Coupe's roof flows more evenly than the sedans, with a less prominent notch where the rear glass tapers downward.Yet all variants share a set of four lines rising from front to rear in or on the body.Rear lamps are similar on Coupe and sedan, as are the rectangular exhaust tips built into the bumpers, rather than hung below them.

Mercedes designers took great pains managing airflow through, under and around the new E-Class, producing a sedan with a drag coefficient of only 0.25, despite its big, brawny appearance.That makes the E-Class the most aerodynamically efficient four-door car in the world, according to Mercedes.The company claims that the Coupe's Cd of just 0.24 is the best overall figure for any series-production car anywhere.Other things equal, a lower Cd means less interior noise and better fuel mileage.

The E-Class wagon will be offered only in Sport trim.That means a bolder three-bar grille, more aggressively flared rocker panels and perforated front brake discs with painted calipers, visible through five-spoke 17-inch wheels.The wagon's roof creates a dramatic teardrop shape in profile, with LED taillights that wrap around the rear corners of the car.

The E-Class Cabriolet comes closest in appearance to the Coupe, except for its power-operated top.The top is traditional fabric, and so well insulated that it actually dampens sound more effectively than the steel roof on the coupe, according to Mercedes.The soft top opens or closes in 20 seconds with one button, at speeds up to 25 mph.

Seat-shaped seat controls high on the door panels and seat heating/cooling controls at the very bottom of the center stack make it easy to adjust important things quickly.Textures and color schemes are familiar Mercedes, too.With the darker interior colors and standard burl walnut trim, the E-Class can create a slightly somber tone inside.Yet in all cases the cabin exudes a classy, understated elegance.

The dashboard in all E-Class variants in identical.The forward door panels and center console are similar as well, though they're trimmed a bit differently depending on the model and equipment ordered.

Mercedes' familiar three-gauge instrument cluster has been supplanted by a package of five analog gauges, including two pairs that overlap each other.All are exceptionally crisp and easy to read at a glance.Nonetheless, the E-Class dash is dominated by something Mercedes calls its COMAND system, which sits front and center at the top of the center stack.

COMAND is a seven-inch color display screen with standard in-dash, six-disc CD/DVD changer and a Bluetooth interface that allows phones to be operated through the car's audio system, even if they remain in a purse or pocket.Using a point-and-click controller on the center console, this central display can be controlled by either the driver or front passenger to adjust audio and other functions.Most features, including climate controls, can be adjusted with their own separate switches lower in the center stack.The COMAND display also shows the optional navigation screen, the back-up camera image, and the night vision infrared display.

The E-Class front seats are new, with a less bulky design that is still quite comfortable and supportive for long stints at the wheel.There's plenty of adjustment in the seats and steering wheel to accommodate nearly any sized driver.The wheel itself is thick and wrapped in nice leather, with multiple buttons to control audio and phone.Mercedes' familiar stalked-mounted cruise-control switch remains, and it still looks too much like, and is too easily mistaken for, the turn-signal lever.The new gear selector is a lot like a turn signal, too, on the right side of the steering column.E-Class cars ordered in Sport trim have paddles behind the steering-wheel spokes for manual gear selection.

All E-Class variants come standard with new active safety features.The big-ticket item is Attention Assist, which constantly monitors up to 70 driving parameters to determine whether the driver is getting drowsy behind the wheel.If it decides a driver is at risk of dozing, Attention Assist uses both visual and auditory warnings to tell the driver to pull over, get some rest, or get a cup of coffee.

The Distronic Plus cruise control option is offered with both blind-spot warning and lane-departure warning systems built in.An intelligent self-adjusting headlamp system uses cameras to detect both oncoming cars and the traffic ahead, and raises and lowers the headlamp beams accordingly.The idea is to put the most light on the road most of the time, without disturbing other drivers.The new Intelligent Nightview option throws infrared light in front of the car and then uses high-resolution video cameras to spot the higher temperatures coming from otherwise invisible pedestrians and animals.

The middle seat in back of the E-Class sedan is reasonably comfortable for a small-to-medium-sized adult on a short trip.The outboard rear seats in the E-Class Coupe are actually a bit more inviting than those in the sedan, even though they're more difficult to climb into in the absence of rear doors.The Coupe's rear seats offer decent legroom, and they're more heavily contoured than those in the sedan.The built-in rear console adds a luxurious, limousine-style touch.

Neither interior nor cargo space in the new-generation E-Class have changed significantly; they are about the same as the previous model's, and the car can be ordered with split folding rear seats for additional cargo flexibility.

Trunk capacity remains at the top of the class, matching the Audi A6 at 15.9 cubic feet, and surpassing the Acura TL (13.1 cubic feet), BMW 5 Series (14.0), and Lexus GS (12.7).The E-Class Coupe has as much trunk volume as the sedan.The E-Class Cabriolet, on the other hand, loses a substantial chunk of trunk space to the storage area for the folded convertible top.

The E350 wagon expands cargo capacity even further, and its standard all-wheel-drive and self-leveling rear air suspension allow a substantial towing capacity of some 2,500 pounds.The wagon features a power-fold mechanism that lowers the split rear seatbacks with buttons near the tailgate, as well as an automatic tailgate that can memorize a desired opening height.The wagon will come standard with a folding third seat in the cargo area when it hits U.S.showrooms in June 2010.

Still, most of these new systems are less intrusive than those in many E-Class competitors.Most functions and features can be adjusted with the point-and-click dial on the center console, or with more conventional, separate switches on the dash: whichever the driver finds easier or less distracting during the process of driving.And, all the new electronic gizmos aside, the 2010 models are more comfortable, more solid, quieter, and more agile-feeling than any previous E-Class.

We particularly like the diesel-powered E350 BlueTEC sedan.Mercedes' V6 turbodiesel is the smoothest, quietest diesel engine available, so virtually all the smoky, clattering drawbacks of more traditional diesel power are gone (though the oily diesel smell during fill-ups remains).Performance is virtually identical the gasoline-powered E350, with even stronger short bursts of acceleration, and the diesel engine comes with a substantial fuel mileage increase compared to nearly every other car in this class.That's good for the pocketbook, the environment and the world's geo-political balance.The BlueTEC 3.0-liter V6 turbo-diesel engine is rated 210 horsepower, 400 pound-feet of torque.

As for the E-Class gasoline engines, both the more economical 268-horsepower V6 and the more powerful 382-horsepower V8 are smooth, quiet, and responsive.Better still, Mercedes' seven-speed automatic transmission is improved compared to previous iterations.It more frequently chooses the perfect gear for the prevailing driving circumstances, and both up or down shifts come quickly.Or the driver can choose the desired gear with the steering-wheel-mounted paddles, and the transmission will stay in that gear right up to the engine's redline without upshifting automatically.

Overall E-Class performance is impressive, regardless of the model, and none of the variants is a lightweight.Packed with all the technology, all the luxury touches and all those airbags, the E350 sedan weighs in at 3,825 pounds and the E550 at 4,034.The 4MATIC all-wheel-drive option adds more weight.Given these figures, the spry acceleration seems even more remarkable.

The E350 V6 will sprint to 60 mph in about 6.5 seconds; the E550 V8 does the same in just 5.2 seconds, with top speed electronically limited to 155 mph, per the German industry agreement to control terminal velocity.

E350 models are powered by a 3.5-liter V6 rated at 268 horsepower and 258 pound-feet of torque.E550 models use a 5.5-liter V8 generating 382 horsepower and 391 pound-feet of torque.

Any E-Class is quick, and made to cruise all day at highly extralegal speeds.All are reasonably nimble.

There's a nice balance of comfortable ride and good handling response, even in the standard models, which put a bit more emphasis on the ride.All E-Class variants have a variable damping system that changes the rebound rate of the shock absorbers according to conditions.This allows a softer, quieter ride on smoother roads, but retains full shock damping through dips, or for spirited driving on twisting two-lanes.

The E-Class brakes are world-class, with the latest electronic controls and built-in automatic braking with the Distronic radar-controlled cruise option.These brakes are consistently powerful at the wheels, progressive and reassuring at the pedal, and they always come back, no matter how hot they may get in a spirited drive.

The E-Class Cabriolet is loaded with features intended to extend open motoring throughout the year.One is AIRSCARF, which uses neck-level heating vents under the headrests.Another is a new device called AIRCAP: an aerodynamic deflector mounted at the top of the windshield.

AIRCAP contains 211 separate parts with 70 patents, and it can be raised roughly 2.5 inches at the driver's discretion to redirect airflow over the top of the E-Class Cabriolet's open cabin.The point? AIRCAP virtually eliminates buffeting (not to mention wind noise) for front-seat passengers when the convertible top is lowered.It reduces buffeting for rear-seat passengers to levels comparable to that experienced by front-seat passengers in other four-place convertibles, according to Mercedes.And it does so without the drawbacks associated with more familiar, screen-type wind blockers raised behind the front seats: reduced visibility, and elimination of rear-seat passenger space.There's at least a slight payback with AIRCAP, to be sure.When the airfoil is raised, the E-Class Cabriolet's roof-open drag coefficient rises from 0.33 to 0.38, and that could have a measurable effect on fuel economy.Nonetheless, AIRCAP works as billed, and allows the quietest, buffeting-free open motoring we've experienced.

NewCarTestDrive.com correspondent Jim McCraw reported from Madrid, Spain, with J.P.Vettraino reporting from Detroit, and Mitch McCullough in Los Angeles.