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Diesel power has come a long way in a short time, with the latest engines becoming quieter, less odiferous, better performing and more compatible with clean-air standards.

Mercedes-Benz takes diesel a step farther for 2009 with BlueTEC, a system that lowers the nitrogen-oxide emissions that are the most objectionable side effect of diesel combustion. The trio of Mercedes vehicles with optional diesel engines – E-Class sedan and G- and M-Class SUVs – now run clean enough to be offered in all 50 U.S. states.

Ultra-low-sulfur diesel fuel, mandated nationwide, makes it possible to equal or surpass today’s gasoline engines in low emissions while delivering the high-torque performance that makes diesel so attractive to truckers.

The ML350 BlueTEC that I drove delivered seamless power without a bit of noisy clatter or oily stink. Whether driving around town or at highway speeds, it was nearly impossible to tell the difference in refinement from a gas engine.

Fuel mileage was a lot better, though. According to the EPA, the ML BlueTEC gets 18 city and 24 highway, compared with the V-8-powered ML550 that gets 13 city and 18 highway. The 3-liter V-6 diesel, with nearly 400 pound-feet of torque, performs comparably with the big gas engine.

I got about 23 mpg, which would represent a savings despite the higher cost of diesel fuel.

The engine performance is attributable to a swarm of technologies, including high-pressure common-rail fuel injection (that’s the CDI); piezo-ceramic injector valves, which provide a fine mist of fuel; and BlueTEC, which uses an oxidation catalyst, particulate filter and injection of a mild urea solution to clean up the exhaust.

Diesel can be compared with gas/electric hybrids in saving fuel and clearing the air, yet still with much less technical complexity.

Vehicle type: Five-passenger, four-door SUV, all-wheel drive.

Engine: 3-liter turbocharged V-6 diesel, 210 horsepower at 3,800 rpm, 398 pound-feet of torque at 1,600 rpm.

Transmission: Seven-speed automatic.

Wheelbase: 114.7 inches.

Overall length: 188.5 inches.

Curb weight: 4,974 pounds.

EPA rating: 18 city, 24 highway.

HIGHS: Quiet ride, strong acceleration, decent fuel mileage.

LOWS: Vague steering, audio complexity, pricey with options.

PERFORMANCE: The engine’s 210 horsepower seems paltry until you consider the 398 pound-feet of torque that comes on at a low 1,600 rpm. The nearly 2.5-ton ML charges like an angry buffalo.

Diesels are inherently low in carbon monoxide and carbon dioxide emissions, so cleaning up nitrogen oxides is the real issue. That urea-injection system, which requires an 8.5-gallon tank refilled every 10,000 miles, seems kind of tacked on. The tank also eliminates space for a spare tire, requiring that ML use pricey run-flats.

The seven-speed automatic is almost a necessity with the narrow power band of the diesel, but it seems right on top of things with seamless shifting.

DRIVABILITY: ML handles well, particularly for a tall heavyweight, but I found the steering to be vague and numb, especially straight ahead at highway speed.

STYLING: Revamped for 2006, the M-Class looks angular and sporty, with a bold grille and an aggressive stance. A nice update of a formerly bland-looking SUV.

INTERIOR: Very accommodating with exceptional space for the front seats, a bit less so in the rear. Fitted with leather and wood trim, the cabin felt solid and luxurious.

Operation of the audio system seemed too complex, especially the process of loading and unloading CDs. Too many buttons to push for a simple function.

BOTTOM LINE: The ML BlueTEC starts out pricey and goes up from there, with expensive options pushing the test car’s price above $60,000.

Base price: $48,125

Price as tested: $61,995.

OPTIONS

Premium package, including navigation, rear-view camera, audio upgrade, power liftgate, Parktronic, Keyless-Go, $6,600.

Leather seats, leather-and-wood steering wheel, burl walnut, $1,995.

Rear-seat entertainment, $1,850.

Air suspension, $1,600.

Bi-xenon headlamps with active curve illumination, cornering fog lamps, LED tail lights, $950.

Shipping, $875.