MANCHESTER, VT – Undeterred by sky-high diesel fuel prices, Mercedes-Benz rolls out three cross/utility vehicles at a global press preview here that boast the auto maker’s first 50-state diesel engine.

The ’09 ML320, GL320 and R320 go on sale this fall with the 3.0L V-6 Bluetec diesel mill that generates 210 hp and 398 lb.-ft. (540 Nm) of torque.

It is the cleanest diesel ever offered in the U.S. and meets Tier 2 Bin 5 emissions regulations.

“Should we put in question our long-term powertrain strategy because of (high fuel prices)?” asks Thomas Ruhl, director of Mercedes’ Bluetec project. “The price of fuel is just one of many parameters in a complex network,” he says. “Fuel prices are not the only crucial factor.”

Mercedes cautiously has attempted to revive interest in diesels in the U.S. in recent years, introducing the E320 Bluetec in 2006 that now accounts for 7% of E-Class sales. “We have the potential to build even further on this success,” Ruhl says.

Mercedes was able to price the Bluetec models at just $1,000 more than their gasoline-powered counterparts because the auto maker makes so many diesels for global markets, Ruhl says.

Diesels cost more to produce than gasoline engines because they require expensive high-pressure fuel injectors and materials that are stiffer and heavier.

Four engineering innovations were used to clean the diesel exhaust in the Bluetec, including an oxidizing catalytic converter, a particulate filter that cuts soot by 98% and AdBlue liquid urea solution.

Cleaning the exhaust doesn’t bite into fuel economy because the diesel generates 20%-33% better mileage than a comparable gasoline engine, Mercedes says. The 6-cyl. Bluetec provides 4-cyl. fuel economy and V-8 power and torque, the auto maker claims, adding the diesel qualifies for the same federal income-tax credit as do hybrids.

Bernhard Glaser, Mercedes general manager-marketing, estimates the ML320 Bluetec will account for 20%-25% of M-Class sales. The percentage will be similar for the GL320, while about 18%-20% of R-Class customers will purchase the R320 diesel.

The average transaction price will be in the high-$40,000s for the ML320; high-$50,000s for the GL320; and mid-$50,000s for the R320, Glaser says.

Mercedes says it is realistic about how U.S. consumers historically have viewed diesels. “People are not just going to flock to diesels,” says Stephen Cannon, vice president-marketing. “It’s not going to happen overnight.”

But Cannon is hopeful the auto maker’s clean diesel will capture some of the same cachet that hybrids have enjoyed in recent years. It’s not unrealistic to believe clean diesel engines will account for about 20% of sales in the U.S. in the next decade, he says.

The biggest opportunities are in California and New York, two of the country’s largest auto markets that have strict emissions regulations, Cannon says.

The ability of the diesel CUVs to achieve a cruising range of up to 600 miles (965 km) is a significant selling point, he adds.

There are 7.4 gallons (28 L) of AdBlue solution in the tanks of the R320 and ML320 that Mercedes claims is enough for 15,000 miles (24,140 km) of driving during regularly scheduled service intervals. The tank in the GL320 holds 8.5 gallons (32 L) of AdBlue.

In a test drive of the CUVs here, there is no discernible difference between the diesel and a gasoline-powered model. The 7-speed automatic transmission shifts smoothly and seems to work well throughout the gear range.

The CUV doesn’t sound or smell like a diesel. There is no perceptible odor, even when lifting the rear compartment that houses the AdBlue solution.

The Bluetec will not be available in the three Alabama-assembled CUVs exported to Europe until next year. Currently, 80% of those vehicles sold in Europe are diesel-powered.