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Answered Prayers: At 22 mpg, diesel power seems like a perfect match for a luxury SUV, but the fuel efficiency doesn’t come cheaply.
We’ve long admired the great fuel efficiency delivered by modern turbo-diesel engines built in Europe. They seem like the ideal powerplants for large and heavy vehicles such as the SUVs that Americans crave when fuel prices are reasonable. A favorite of ours in this category is the Mercedes GL, so when a diesel V-6 was added to the lineup with the 2008 models, we decided to see how it would work in the U.S.
The GL320 CDI, as the diesel is designated, was the least expensive model in the GL line, with a base price of $53,775 when it was delivered in August 2007. At that price it comes equipped nicely, but we also specified several options to make it even more comfortable. The Premium 1 package ($6400) added a rearview-backup camera, parking sensors, a glass sunroof, a navigation system, satellite radio coupled to a better sound system, and a power passenger seat, steering column, and liftgate.
We also selected the rear-seat entertainment package ($2670) with dual second-row screens to pacify children on long trips and the Keyless Go package ($1110) to relieve us of the burden of having to fish for the car’s key fob in order to open the GL’s doors and start its engine. The Heating package ($895) let us warm the steering wheel and the rear seats (front-seat heaters are standard). “Barolo” paint added $710. We also ordered the $510 Towing package, along with a $510 voice control to make it easier to program the nav system, and finally, a $375 iPod-integration package. It came to $66,955—far from cheap but within the range of competitive large luxo SUVs.
Curious about this car’s key feature, the crew here quickly found the diesel engine to be very satisfying. Overall, we averaged 22 mpg with the GL, which is terrific for a vehicle that’s about the same size and heft as a Cadillac Escalade. It didn’t much matter whether we drove the GL320 in town or on the highway, the mileage stayed consistently in the low 20s, rising to the mid-20s if we kept our highway speed below 75 mph.
When the GL first arrived, we were concerned that finding the requisite ultra-low-sulfur diesel fuel might be a problem, but it turned out to be everywhere. It was even in supply at one particular gas station in Lancaster, Pennsylvania, where the diesel pumps did not carry the ULS label and the humanoids at the gas stations had never heard of the stuff.
The characteristic diesel rattle and smoky exhaust are minimal in the GL. At startup in the morning—which never required a long glow-plug wait—we noticed that the oil-burning V-6 is a little louder than a gasoline engine, especially if you’re in an enclosed garage. But once under way, the rattle quickly fades. Similarly, we only saw a touch of smoke during cold starts.
Full Article: 2008 Mercedes-Benz GL320 CDI 4MATIC - Long-Term Road Test
M
Simply amazing! 
