2011 Mercedes-Benz R-Class

2011 Mercedes-Benz R-Class

2010 Mercedes-Benz ML450 Hybrid

2010 Mercedes-Benz ML450 Hybrid

Mercedes-Benz offers a clean-diesel Bluetec version of each of its large utility vehicles, the R-Class, GL-Class, and M-Class, along with a Hybrid version of the ML. But even combined, the standard gasoline versions of these vehicles are still far outselling their greener counterparts that don't cost much more.

In the case of Mercedes' R-Class luxury people-mover, only about five percent in the U.S. are purchased in Bluetec form—even though the 2010 Mercedes-Benz R350 Bluetec costs just $1,500 more than the V-6 gasoline R350 (2011 prices are pending but won't change significantly).

We find that a little puzzling, as after a First Drive of the spruced-up 2011 Mercedes-Benz R-Class last week posted at The Car Connection, the R350 Bluetec in particular remains one of our favorite long-distance road-trip vehicles. With its cavernous interior and adult-size seating for six (or up to seven), the R-Class is a step above minivans for anyone who places the priority on passenger comfort. And with the diesel it has plentiful load-stomping torque yet can return fuel economy in the mid-20s—quite the feat considering its 5,000-pound-plus curb weight.

No way around it, the R-Class has been a slow seller. M-B has sold around 3,000 R-Class models per year in the U.S. It sells many times more boxy GL-Class utes, and some months its M-Class sales have exceeded annual R-Class sales. But even for the slightly truckier (in image) GL and ML models, roughly 12 percent are Bluetec diesels.

Slow sales, despite plenty of arguments pro

Among older M-B models, diesels have had much better resale value, so combined with the better fuel economy and drivability we find the economics a no-brainer.

As a surprising number of shoppers still turn their noses up to diesel, Mercedes-Benz is covering all the bases; in addition to its Bluetec, the ML450 Hybrid first went on sale—or rather, on lease—late last year. The automaker is only offering it under a special lease, either at $659 per month for a 36-month lease or $549/mo. for a 60-month lease.

With a 275-hp, 3.5-liter V-6, and an electric motor system that brings output to a combined 340 hp, the ML450 Hybrid has roughly the same power as the gasoline V-8-powered ML550, while its EPA ratings are 21 mpg city, 24 highway. The packaging isn't any different than the standard ML, as the liquid-cooled nickel-metal-hydride battery pack is stored under the rear cargo floor.

But so far, the ML450 Hybrid hasn't exactly been screaming off lots either; the automaker has only been moving about 80 of ML450 Hybrid models per month.

Where did the demand for greener vehicles go?

Sheryl Crow loves BlueTEC

Sheryl Crow loves BlueTEC

Back in the 1980s, more than 75 percent of Mercedes vehicles sold in the U.S. were diesels—and that was when they were dirty and had dubious drivability in some cases. In recent years, all the pro-diesel buzz somehow hasn't materialized in sales, even when the products are genuinely night-versus-day better: quieter, cleaner, more powerful, and more refined. Mercedes-Benz officials explicitly told us that, especially in the case of the Bluetec models, it's a question of demand, not supply, and that it would return to a higher level of diesels if the market supported it.

What do you think? Why are so few luxury utility buyers interested in diesels (or even hybrids) today?