Mercedes-Benz GL320 BlueTec--Feeling a bit AdBlue over spending a lot of green

It wasn't enough that our GL320 is feeling a bit inferior now that Mercedes-Benz changed its name to GL350. (No, the displacement didn't increase--even the GL320 designation was something of a fib, given the engine was a 3.0-liter.)

Around 16,000 miles, our GL displayed a warning light saying that it was running low on AdBlue. This urea-based additive is necessary to keep the turbodiesel emissions-compliant; it is injected into the exhaust tract to break down smog-producing nitrogen oxide into nitrogen in a catalytic converter.

Normally the AdBlue would have been topped off by the dealer at a regular oil change. But with 80+ cars here each year, and multiple lifts and mechanics, it would be a needless hassle and expense to take every car to the dealer to change the oil. Since we had changed our GL's oil ourselves, we wound up making a trip to the dealer to get AdBlue added. (We also had to get a shorted-out taillight repaired under warranty, plus get a software update and recall addressed.)

The total bill just for adding AdBlue? A stunning $316.99. We were down to 18% full on the additive at 16,566 miles. It took 7.5 gallons to fill the tank, costing an eye-opening $241.50 for the fluid alone. The labor to add the fluid plus tax accounted for the rest. None of this was covered by the warranty.

There are virtues in buying the diesel GL Class. It's the least expensive GL, which is a very nice SUV (even if it isn't reliable in our survey data). And the recorded 19 mpg overall in our tests is pretty good for a three-row SUV -- even if that just rivals a more prosaic minivan's fuel economy. You also have an impressive 615-mile cruising range. The diesel provides sub-10-second 0-60 mph times and appealing mid-range torque. You could even get a tax break.

But let's extrapolate the AdBlue budget. At the current rate and cost of consumption, just the AdBlue itself (without the labor, which would probably be included as part of the routine service) would cost $1,457.80 for 100,000 miles of driving. That's a lot of money, knocking about a third off of your fuel savings vs. buying a GL450 V8. (You can't buy a gasoline-powered V6 GL).

Our AdBlue consumption might be a bit on the high side. After all, Mercedes says AdBlue consumption will be increased in "more demanding situations e.g. when towing a trailer," and I did use the GL320 to tow my T@B teardrop for a few hundred miles. (I got about the same mileage and performance towing it with the diesel as I do with my Honda Odyssey.) Our acceleration tests probably also took their toll. But these activities didn't account for the bulk of the GL's miles, so our usage probably isn't that far off.

Maybe it isn't a surprise that keeping a $67,000 Mercedes-Benz turbodiesel SUV on the road will cost a lot of money. But it just adds to our argument that offering diesels in mostly luxury models here in this market (VW's TDI is a notable exception) isn't helping put their best foot forward. It also makes BMW's offer of free maintenance (including AdBlue) up to 50,000 miles look more enticing.