According to Mercedes-Benz, the 2007 E320 BlueTec has an "unprecedented regard for the environment." Making use of the clean-diesel technology pioneered by DaimlerChrysler in Europe (and recently adopted by Volkswagen and Audi), the 2007 Mercedes-Benz E320 BlueTec is the first in a new generation of diesel cars that aims to replace the stereotype of diesel engines as smog-spewing smokestacks with one of a clean and efficient alternative to gasoline engines. With all the upscale refinements we expect from Mercedes, the stylish and comfortable E320 BlueTec is the ideal Trojan horse for the next generation of diesel engines in the United States.
Test the tech: Beverly Hills and back or bus
For our tech test of the 2007 Mercedes-Benz E320 BlueTec, we decided to see just how efficient its diesel engine really was. Armed with the EPA estimates that showed the V-6 seven-speed automatic E320 was capable of 37mpg on the highway, we devised a road trip to the furthest point from the CNET headquarters in San Francisco to which we could drive to and back on one tank. Having done some calculations based on the size of the E320's fuel tank (21.1 gallons) and the estimated highway mileage (we agreed on the Mercedes estimate of 35mpg rather than the more optimistic EPA rating), we figured that the farthest we could go on one tank would be about 757 miles, assuming that we managed to maximize fuel economy for the entire trip. A dig around on Google Maps showed us that the Beverly Hilton hotel in Los Angeles is 377 miles away, making for a round trip of 754 miles: perfect.
Needless to say, our driving was not going to be all open freeways and deserted city roads, and so we figured we would just have to ride our luck in terms of negotiating the traffic on both ends of the journey, and maximize our mileage by using a number of economical driving techniques on the freeway.
Setting out from San Francisco, the navigation system suggested that the route we should take to L.A. was over the San Francisco Bay Bridge onto Route 580 and then down Interstate 5 all the way to our destination. Not wanting to have to negotiate the ubiquitous rush-hour bottlenecks on the bridge, however, we decided to go our own way and take Highway 101 all the way down the coast instead. Unbeknown to us at the time, this would ultimately prove to be a critically influential decision.
We realized before we set out that one of the major challenges in our epic drive was going to be keeping the car moving at a steady rate, without too much braking or accelerating. To help us achieve this, the E320's cruise control, activated by a stalk above the left turn-signal lever, let us set, increase, and decrease speed with relative ease. By the time we had reached San Luis Obispo halfway between San Francisco and Los Angeles, we had achieved an overall mileage of 37.8mpg over the first 232 miles according to the instrument-cluster mounted LCD readout from the trip computer. So far, so good. On the remainder of the journey to L.A., we maintained this better-than-estimated fuel economy, at times even seeing the mileage rise above 38mpg. Arriving at our hotel, we had maintained an average fuel economy of 37.5mpg over 436 miles and over 7 hours and 18 minutes of driving.
It was at this point we realized that by taking route 101 we had added more than 60 miles to what was already a challenging distance for one tank of fuel. Setting out from L.A. on the return journey (this time on Interstate 5), we realized we needed to get even better mileage on the way back if we were to make it home without filling up. Unfortunately, traffic was not on our side, and we spent about an hour cursing the stop-and-go traffic streaming north on Route 405 out of L.A. By the time we were up to speed on Interstate 5, we had 306 miles to go to get back to San Francisco according the navigation system, while the E320's trip computer told us that we had 193 miles until empty.
The range-to-empty did briefly increase for a time, and at one point of downhill driving the one-tank journey seemed possible. However, when we got back on level road, the range-to-empty dropped significantly, and we realized we would have to refuel. When we finally did fill up, the car had done 638 miles and the onboard computer estimated we were still good for another 93 miles. Our overall mileage--achieved in predominantly freeway driving at 70mph, with an hour of so of nose-to-tail city driving--came out at 36.8mpg; a phenomenal fuel economy for a full-sized luxury sedan.
In the cabin
The interior of the 2007 Mercedes-Benz E320 BlueTec has many of the same luxury appointments and tech features as those we saw in the 2007 Mercedes-Benz E550. Coddled in leather seats and surrounded by burled walnut trim, it was clear that whatever changes had been made under the hood, the interior of this car is unmistakably Benzian. For those looking for more luxury than the garden-variety opulence of the standard trim level, a choice of two optional "designo" trim packages offer a combination of metallic paint, Nappa leather upholstery, a wood steering wheel, and leather-trimmed floor mats for a cool $6,400 on top of the sticker price.
As with most upscale Mercedes models, the E320 BlueTec comes with the Comand system, a catchall for most digital cabin technology features, including navigation, audio, and climate control. As we made clear in our review of the 2007 E550, we are not great fans of the navigation systems in the E-Class. The LCD screen is set very low down in the central stack, making it directly in line with the natural resting place of the driver's right hand on the steering wheel. This problematic placement is compounded by the screen's dullness and the unfortunate blue-on-blue color scheme that is used for most menus.
Adding to the woes of those trying to use the navigation system on the fly is the fact that many of the menu functions are not labeled, meaning drivers have to speculatively press 1 of the 10 mode-dependent buttons on either side of the screen to first get a menu and then make a selection. Trying to zoom in on the map, for example, required us to press any button, bringing up a menu, and then repeatedly press one of two buttons approximately aligned with the onscreen options on the far side of the screen to zoom in or out.
Programming destinations into the navigation system is equally cumbersome, as it requires lots of fiddling about with the multidirectional button cluster on the lower right of the screen. Letters for place names or points of interest must be selected and entered one at a time, a procedure that is lengthened further by the navigational system's sluggish processor (fiber-optic communications network appears to offer little help), which has a habit of stopping for a long, hard think between menu levels and sometimes between individual letter entry.