Mercedes-Benz, as the inventor of the diesel passenger car in the 1930s, has an unspoken obligation to lead and innovate. In this role, the automaker has been steadily adding to its U.S. lineup of diesel-powered automobiles since introducing the first BlueTec engines back in 2006, most recently with E-Class and S-Class diesels.

In the M-Class, Mercedes-Benz currently offers one diesel variant, the ML350 BlueTec. Similar to the other diesel Mercedes sold in the U.S. the ML350 BlueTec uses AdBlue urea injection to scrub the exhaust and meet emissions requirements in all 50 states. The AdBlue system injects the urea solution into the exhaust flow. which in turn releases ammonia turning order to convert nitrogen oxides into harmless nitrogen and water in the catalytic converter. (The AdBlue tank typically needs a refill every 10,000 miles.)