That prompts the question: Can there be a new-generation car if there is no generation gap? Or is that the automotive equivalent of the rhetorical question: If a tree falls in the woods and nobody is there to hear it, does it really make a sound?

The sound, or more accurately the lack of sound, is one of the impressive features of the new E-Class, which has enough significant improvements to justify Mercedes giving it its own generation, and also to summon a couple of waves of automotive journalists to the Napa Valley area, 100 miles north of Sacramento, to examine and drive it – even while acknowledging that the outside underwent more of a mid-cycle refresh than a redesign.

It didn’t take more than one step on the gas to appreciate the tremendous power and the firmer handling of the new E550, but for style, the existing 2006 E-Class certainly won’t look out of date next to the 2007.

The new car’s grille is slightly taller, leans back at a steeper angle, and wears a new small Mercedes emblem just ahead of the traditional Mercedes star hood ornament. Below the grille is a pointier front bumper – the easiest way to differentiate the two. If the bumper comes to a distinct point at its leading edge, it’s the new car.

Taillight lenses have a smoother lens, which is interesting, because the current style’s grooves were designed to force airflow and rainwater to clean off the taillights.

New side mirrors have an air-channeling design to help blow the side windows clear of rain.

The first E-Class sedan was built in 1953, and it evolved into the company’s "bread and butter" car, particularly in the last dozen, when it usually outsold the more compact C-Class and the larger S-Class.

The new E reflects Mercedes’ continued attempt to divide and conquer with the usual Luxury model to satisfy the discriminating taste of the car’s traditional minions, and adding a Sport, which will attempt to swipe some performance/luxury customers from the likes of the BMW 5-Series, Audi A6, Acura RL or TL, Infiniti M, Lexus GS450h, or Cadillac STS.

Bernhard Glaser, general manager of product management, said the two-pronged approach with Sport and Luxury models worked with the C-Class, and led to the same strategy with the E-Class. He noted that traditional buyers will find all they expect, plus some added dynamic function, with the Luxury model, while the Sport model seeks to lure performance buyers who don’t mind a firmer suspension in exchange for more precise handling.

In reality, both cars do their best to close even that gap. The Luxury model rides a bit softer but still handles very well on its new suspension, while the Sport model – available on either the E350 V6 models or the E550 V8 models -- handles with a flatter attitude on its firmer air-suspension, without ever approaching harshness, despite riding 1.5 inches lower and on 18-inch alloys compared to the Luxury’s 17s.

Both models benefit from the new suspension, with asymmetric control arms enhancing lateral support, and a new steering system, which is 10-percent more direct in responding. Inside, the Sport gets white gauges, and two unique interior packages – black bird’s-eye maple trim instead of the Luxury model’s rich burled walnut.

The Sport also has specific interior trim, either black with Sahara beige leather seats, or black with cognac brown leather. The Sport windows have a bluish tint, to differentiate from the neutral green of the Luxury.

Remarkably, the Sport model costs no more than the Luxury. In either form, the base price of the E350 is $50,550, while the E550 will start at $59,000 when it hits the showrooms in September.

The new V8 engine is the latest gem from Mercedes, which had gone to a smooth and efficient three-valve engine system for its V6 and V8 over the past decade, using two intake valves and one exhaust on each cylinder, operated by a cost-effective single overhead camshaft on each bank. Last year Mercedes changed to four-valve heads with dual overhead cams on the V6, and its increase in power and fuel-efficiency moved close enough to the V8’s performance to be a wise alternative.

This year, Mercedes has applied the four-valve, DOHC concept to the 5.5-liter V8 as well, and it makes a particularly notable difference in the E550.

The new V8 has 382 horsepower – an increase of 80 horsepower (26 percent) -- and 391 foot-pounds of torque – an increase of 52 (15 percent). No less than 100 percent of that torque is available from 2,800-4,800 RPMs, and 75 percent of the torque can be summoned at 1,000 RPMs, barely above idle. With the slick seven-speed Mercedes automatic transmission and its manual-selection capability, the E550 meets or exceeds every expectation for power.

That E350 V6 now has 268 horsepower and 258 foot-pounds of torque – more than adequate, and the E350’s 0-60 times of 6.5 seconds are not that far off the E550’s 5.4-second clocking.

This fall we can look forward to the same car becoming available as an E320, with a 3.0-liter Bluetec turbo-diesel, generating 208 horsepower and a startling 388 foot-pounds of torque, with 0-60 times at 6.6 seconds. That patented Bluetec diesel will thrive on our newly cleaned low-sulfur diesel fuel being put in place between now and October, and could be a third prong for Mercedes.

While we’re at it, we must also point out a fourth as well, because for the first time, the in-house AMG performance branch of Mercedes got a chance to build an engine from a blank sheet, rather than merely modifying a production engine. The result is the limited-production E63, extracting 507 horsepower and 465 foot-pounds of torque from 6.3 liters, and Porsche/Ferrari/Corvette Z-06–like acceleration of 4.3 seconds.

It only took us one stop to marvel at how quiet the muscular 5.5 V8 runs. I had driven just over an hour through the scenic, curving roadways in the Northern California mountain range when we arrived at a restaurant parking lot for a prescribed rest stop and driver change.

The car has the keyless operation system, whereby if you have the key in your pocket, the car unlocks itself as you approach, and you can start it by push-button, on top of the gearshift lever, which makes me nervous. As I pushed down on the gearshift’s handgrip button to shut off the engine, I mentioned to my codriver that it was neat, but it bothered me. On many cars, a very similar button must be pressed to shift out of park; in this car, that move kills the engine.

To demonstrate, I pushed the button down three or four times in a row, at five-second intervals, alternately starting and shutting down the 5.5-liter V8. As we climbed out, my codriver asked if the car was still running. "No," I said, "that’s just the fan, cooling down the engine."

He nodded and said "OK, I just wasn’t sure." Thermostatic fans run on sometimes, after hard driving, and we could hear the soft hum as we walked around to the rear of the car, nodding to three Mercedes officials positioned there.

Inside, we had some coffee and munched on snacks, and in 15 minutes we were ready to resume our drive westward, through the redwood-lined mountains to the coast. We stopped casually to talk to the same three Mercedes folks still standing a few feet behind our car. Then we climbed inside the E550.

Only then did I notice the, uh, fan seemed to be still purring along, so I pushed down on the gearshift knob button. Sure enough, it stopped. The engine had been running the whole time. It was so quiet-running that both of us drivers, as well as several Mercedes officials standing just starboard of our tailpipes, didn’t notice that the engine was running.

Those keyless operation deals, where if you have the key, you don’t need to use it, either to unlock the doors or to start the car, concern me for other reasons. I always envision driving to the airport, jumping out to catch a plane, while turning the idling car over to my wife or son.

While they’re driving home, I notice the key is still in my pocket – at 40,000 feet above Denver. I like the feature of the door automatically unlocking as you approach, but if you need to have the key to start the car, I think not needing to put it into the ignition switch is like designing a neat cure for which there is no known disease. Embarrassing or not, inadvertently leaving the car running during lunch verifies my concern.

When we were certain the E550 was running intentionally, we fairly flew up the mountain roads, around the tightest switchbacks, through the giant redwoods, and along the fabulous Pacific Coast vista of California 1, which winds up the Pacific coastline all the way past Mendocino.

We switched out of the E550 Sport to the E350 Sport for the afternoon driving assignments, and we were in for another surprise.

The power of the E550 V8 was awe-inspiring, but in spirited driving, if you go hard into a tight curve and hit the gas, the beast wants to show off its power by jumping ahead with startling suddenness. Impressive as that power is, you have to be focused on doing some steering correcting as you fly around tight curves.

For real-world consumers, doing real-world driving, the E350 in some ways was more precise, felt more agile, and seemed to harmonize even better with the quick-steering and handling balance. , You could hammer it hard through the same tight curves and it tracks smoothly and predictably.

After a few such curves, I could throw the E350 Sport into a turn knowing it would track precisely without steering correction, without concern that a heavy foot might cause the car to zoom ahead harder than you intended.

From the driver’s seat, the trip computer registered another key difference. Driving to excess in the E550 showed an impressive 19.8 miles per gallon, highway and curves, although it certainly would get better on a normal commute.

The E350 indicated 26 mpg, also when driven hard, and also with an anticipated improvement in moderate, everyday driving. That closes the inter-model gap further, and the Bluetec diesel will narrow it more, even if the AMG model stretches it a bit.

Driving through the redwoods of Northern California, we paused to marvel at the majestic and enormous old trees. It reminded me that a week earlier, my son, Jeff, and I had marveled at the size of some huge old Douglas Fir trees in Northern Washington State. I also was reminded of Jeff’s comment: "

These things are so huge that I have the feeling if one of them fell over, there would be some noise – even if nobody was around." Similarly, we must concede that the E-Class will thrive in a seventh-generation mode, even without much generation gap.