First Drive Review
Now that we have the cleaner, ultra-low-sulfur diesel fuel in the U.S., Mercedes-Benz is unleashing a wave of diesel models. Analysts predict that diesels will make up nine percent of the U.S. market in 2013—up from just two percent in '05—and many automakers are promising diesel models in the near-future. Mercedes reports that about 15 percent of its M-class SUV customers are opting for the diesel ML320 model since it went on sale in October of 2006.
Mercedes' 215-hp, 398 lb-ft 3.0-liter V-6 turbo-diesel is teemed with the seven-speed automatic transmission and is now available in four models including the E-class sedan as well as the R-, M-, and GL-class sport-utes. But, the diesel option in the large, seven-passenger GL makes the most sense. Why? In the other three cases, a V-6 gasoline engine is the base option, with the diesel costing an extra $1000. While you may think that's not much money for a 30- to 40-percent boost in fuel economy, it will still take tens of thousands of miles to make back that initial investment.
In the comparison-test-winning (Top-Rung Sport-Utes, October 2006) GL-class, however, the GL320 diesel is actually the cheapest in the lineup, the only other choice is the GL450 with a 335-hp 4.7-liter V-8. Starting at $53,175, the diesel GL actually saves $2500 as well as boosting fuel economy ratings by 40 percent—from 14/18 city/highway to 20/25.
Don't worry; there are almost no downsides to the diesel GL, it will still tow 7500 pounds, same as a GL450 and more than the 403-hp Escalade. Okay, so the diesel won't shoot to 60 mph in 6.6 seconds like the GL450, but who needs to their large, people-hauling SUV to hustle like that anyway? We figure the GL320 will do the 60-mph deed in around nine seconds, but it's certainly not hurting for power. There's always a strong pull from the torquey diesel engine—well past legal speeds, we assure you—even though the diesel's constant moan under acceleration isn't nearly as exhilarating as the V-8's. Once up to speed, however, the engine noise fades to nothing, making the GL320 a serene and superb highway cruiser.
We averaged 24 mpg over a 160-mile mix of city and highway roads, and even with frequent excursions to the 4600-rpm redline it seemed hard to ever dip below 20 mpg—not bad for a 5500-pound beast that will hold seven adults comfortably. That's a 33-percent improvement over the 18 mpg that the GL450 in our comparison test managed while it was beating out all of its peers, including the Audi Q7, Cadillac Escalade, and Infiniti QX56.
