Mercedes' Luxury Diesel SUV

The Mercedes-Benz GL320 CDI could change the way Americans think about diesel. Mercedes certainly hopes so

by Thane Peterson

Editor's Rating:

The Good: Seven-passenger seating, 24 mpg on the highway, standard all-wheel drive

The Bad: Premium price, high cost of diesel fuel

The Bottom Line: Considering downsizing from a big SUV? Mercedes suggests going diesel instead

Reader Reviews

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Up Front

If you want to drive a big SUV and get halfway decent mileage, you have a choice this year: hybrid or diesel. General Motors (GM) is the pioneer in big hybrid SUVs with new gasoline/electric-powered versions of its Chevy Tahoe (BusinessWeek.com, 3/3/08), GMC Yukon, and Cadillac Escalade. Meanwhile, Mercedes-Benz (DAI) and other German companies are coming out with a raft of attractive diesel SUVs, of which the new Mercedes GL320 CDI is a prime example. It is a roomy seven-passenger all-wheel-drive vehicle rated to average 20 miles per gallon (18 city/24 highway), one-third better than the Mercedes GL450, the most comparable gasoline-powered model.

Diesel, which accounts for about half of the European market, seems destined finally to gain popularity on this side of the Atlantic. It will account for only 3.6% of U.S. passenger vehicle sales this year (vs. 2.4% for hybrids), but J.D. Power & Associates expects diesel's share to rise to about 10% by 2015. Mercedes saw its U.S. sales of diesel-powered models increase by 81.2%, to 12,580, last year. Its diesel-powered products include M-Class, R-Class, and GL-Class SUVs, as well as an E-Class sedan (BusinessWeek.com, 6/30/06).

One of the big impediments to diesel's success is about to be removed. Current diesel SUVs can't be sold in states with stringent pollution standards, including California and New York. As of this fall, when '09 models come out, Mercedes diesels will burn clean enough to be sold in all 50 states for the first time. Later this year, BMW (BMWG) is unveiling its '09 X5 xDrive 35d, a diesel-powered version of its hot-selling X5 (BusinessWeek.com, 4/27/07), and Volkswagen (VLKAY) and Audi (NSUG) with a V-6-powered versions of the Touareg TDI and Q7 TDI, respectively. These new diesel SUVs will also qualify for sale in all 50 states, the companies say.

One big downside remains. Diesel—which historically cost less than regular gasoline—has been selling for around $3.70 per gallon lately, according to the American Automobile Assn., about 20¢ more than premium gasoline and 50¢ more than regular unleaded. The price of diesel may come down after the costly transition to clean-burning ultralow sulfur diesel is completed in 2010, but that's far from certain. High demand from China, India, and Europe, as well as a shortage of refinery capacity in the U.S., could all maintain upward pressure on prices.

Fuel price jitters aside, modern diesels are far more attractive than the loud, smoke-belching diesels of yesteryear. The GL320 CDI starts easily in cold weather. Outside the vehicle, the idling engine has a noticeable grumble, but during driving it makes no more noise than a gasoline engine. The 3.0-liter V-6 in the GL320 is rated at only 215 horsepower, but like other diesel engines it delivers far more torque (398 foot-pounds) than a comparable gasoline engine, giving it excellent towing power and surprisingly good acceleration.

To my eye, the GL's exterior styling is less attractive than that of Mercedes' more popular M-Class. The GL looks too square and panel-van-like for my taste. But it's a wonderful piece of machinery, with four-wheel independent air suspension with electronic damping, a unit body chassis made of high-strength steel, and Mercedes' usual full array of air bags and other safety gear.