Driving Impressions

By January 6, 2006

The new V6 engine that comes on the 2006 Mercedes-Benz E350 addresses one of our primary gripes: disappointing performance from the standard engine. The new engine is slightly larger (3.5 liters vs. 3.2), and it's the first Mercedes V6 with dual overhead cams and four valves per cylinder. The 3.5 liter V6 generates 268 horsepower (20 percent more than the 3.2) and helps trim fully half a second from the E350's 0-60 mph times.

More important, matched with Mercedes' high-tech seven-speed automatic transmission, the new engine makes the E350 generally more responsive than the 2005 E320. The 3.5-liter V6 has fully variable valve timing, delivering an impressive amount of torque from idle all the way to the redline. The E350 responds much more immediately, with more obvious acceleration, than the old E320, no matter how fast it's already traveling when the driver dips the gas pedal. The new engine is also noticeably smoother, particularly at high rpm. And thanks to the seven-speed transmission, the improved performance comes without a corresponding decrease in fuel mileage.

The diesel-powered E320 CDI is impressive. Its turbocharged inline six-cylinder diesel features all the latest high-tech goodies, including CDI, the common-rail direct injection system, which delivers fuel to the engine at an incredible 23,000 psi, compared to 100-250 psi in a typical gasoline engine. Yet the technology matters far less than the results. Forget everything you know about diesel-powered cars built in the 1970s, '80s or '90s. Slow starting? Not anymore. Like all diesels, the E-Class version still needs electric glow-plugs to heat the combustion chambers before starting. Yet during our week-long evaluation, in early spring in the Midwest when mornings are more than cold enough to leave a coating of dew on the landscape, the E320 CDI never started more slowly than a gasoline engine.

Unpleasant odors? You'll still get that oily diesel smell when you fill the E320 CDI's tank, but once the filler cap is back on and the car is running, you'll notice no unpleasant fumes inside or out of this E-Class. Excessive engine noise? At idle, during warm-up, you'll hear the rapid tick-tick of diesel noise more loudly than anything coming from the gasoline-powered E350's engine. But once the diesel is warm, there's very little difference in the amount of engine noise reaching the cabin compared to other E-Class models. The diesel engine is also surprisingly smooth, and the extra bit of noise comes with some excellent benefits.

Start with outstanding fuel economy. According to the EPA, the E320 CDI beats its gasoline-powered counterpart by more than 10 miles per gallon for both city and highway driving, estimated at 27 and 37 mpg respectively. Our test suggests that a 10 mpg edge overall is easily achievable in the real word. With predominantly highway travel, the CDI has a range of 600-700 miles per tank, so owners won't have to tolerate the smell of diesel fuel very often. With gasoline topping $2 a gallon, and the mileage advantage of the E320 CDI, the paradigm for the typical American buyer may finally have shifted toward diesel engines.

Why? Because the E320 CDI performs just as well as the gasoline powered E350. Its 201 horsepower is impressive by diesel standards, but that's not the half. This engine produces a whopping 369 pound-feet of torque, more even than the E500 gasoline V8, and it's the twisting power of torque that generates acceleration. Dip the accelerator pedal on the E320 CDI and it jumps, quickly enough to spin the back tires just by jabbing the gas if you switch the traction control off. Before the introduction of the new 3.5-liter gasoline V6, the CDI would leave the standard gasoline-powered E-Class in the dust. Even now, it will run neck and neck with the E350, up to about 90 mph. Moreover, the CDI engine breathes freely enough that it keeps pulling strong up to the tr