In Woody Allen鈥檚 1973 sci-fi send-up Sleeper, his character finds a 200-year-old Volkswagen Beetle in a cave and starts the engine, which turns over without the slightest hesitation. Allen could have substituted a W115 Mercedes 200D in the same ridiculous but truth-based scene. Mercedes-Benz diesels, like air-cooled VW flat-fours, are pretty much indestructible. Now, Mercedes has released a new generation of its venerable four-cylinder diesel. The latest OM 654 2.0-liter turbo-diesel four-cylinder debuts in the Euro-spec 2017 E220d this spring, and sometime later in the U.S. It replaces the OM 651 2.1-liter diesel in service worldwide since 2008, although our time with it was considerably shorter; it arrived here in 2013, first in the GLK250, and then in the E250 and ML250 BlueTec models. Of that engine鈥檚 three strengths offered in Europe (250, 220, and 200), we received only the most powerful. The new engine鈥攊n 220 strength at least鈥攎akes 195 horsepower at 3800 rpm (up 25 hp) and 295 lb-ft of torque between 1600 and 2400 rpm.
Compared to our current 2.1-liter engine, it achieves the same horsepower but nowhere near the 369 lb-ft that made our 2014 E250 sedan sneaky fast. Mercedes hasn鈥檛 confirmed U.S. 鈥檒l bet our version will produce more torque. More so than output, the big news is the OM 654鈥檚 cast aluminum block, as Mercedes is waving goodbye to the trusty cast iron block for four-cylinder diesels. This helps the new engine save a claimed 101 pounds (with all mounted accessories) versus the OM 651 220-spec diesel. Mercedes also used aluminum for the oil pan, reduced cylinder spacing by 0.16 inch, removed the second series turbocharger in favor of a single setup, and switched to plastic engine mounts, which reduce both weight and vibration. Each of the cylinders displaces 0.5 liters鈥攎any manufacturers believe this volume provides max power and efficiency鈥攁nd is lined with slippery Nanoslide, an iron-carbon coating on the cylinder walls that cuts friction. For the pistons, Mercedes engineers chose steel instead of aluminum, leveraging the metal鈥檚 lower conductivity to improve combustion at higher temperatures and reduce friction between 40 and 50 percent. This is possible since aluminum, when hot, expands at a higher rate than steel, so the more tightly controlled clearance between the steel piston and the aluminum cylinder wall becomes especially advantageous, according to Mercedes. In the wake of the VW TDI scandal, we can鈥檛 talk about a diesel engine without bringing up exhaust emissions. Here, Mercedes installed all of the after-treatment components within the engine compartment. Instead of particulate filters and a trunk-mounted urea tank located downstream, these parts are installed on the engine itself. We don鈥檛 yet know how efficient the new engine is, or when it鈥檒l appear in the new E-, GLC-, and GLE-class models. The brawnier 3.0-liter turbo-diesel V-6 currently in the full-size GLS350d isn鈥檛 going away. And thankfully, neither is Benz鈥檚 commitment to any of these hardy, longlasting oil-burning engines.
Normally, stating that a new or updated car is just like its predecessor kind of saps the life out of its 鈥渘ewness.鈥?Take the 2017 Mercedes-Benz GLS450, for example. Its close kinship with last year鈥檚 GL450 may not be exciting, but it is a good thing, as that model represented the ideal intersection of price, performance, and fuel economy in the four-model GL-class lineup. For 2017, that family stays the same aside from a minor name change to GLS-class and subtle cosmetic updates inside and out. Sharing its 362-hp 3.0-liter twin-turbocharged V-6 with the pre-refresh, S-less GL450, the GLS450 again slots into the lineup above the diesel-powered GLS350d and below the high-powered, high-priced, eight-cylinder GLS550 and GLS63 AMG variants. 1650 over a GLS350d, and for that extra scratch you get 107 more horsepower at the expense of a few mpg. GL350 diesel and the GL550, the GLS450 compares favorably. The GL350 BlueTec reached 60 mph in 7.5 seconds and returned 22 mpg, while the GL550 accelerated to 60 mph in 5.4 seconds but delivered a dismal 14 mpg. Aside from their new nine-speed automatic transmission shared with the GLS450, the 鈥?7 GLS350d and GLS550 aren鈥檛 expected to perform much differently.
For its part, the new GLS450 smoked to 60 mph in 5.7 seconds鈥攋ust a tick behind the 550鈥攚hile its observed 18 mpg was much closer to the diesel than to the V-8. Those in slightly less of a hurry could argue a strong case for the diesel, as well. The GLS450鈥檚 new transmission is dubbed 9G-Tronic. Its first seven gears sport shorter ratios than all seven speeds in the old transmission. Compared with a 2015 GL450 we tested last year, the GLS450鈥檚 spicier gearing enabled it to reach 60 mph 0.2 second quicker and post snappier 30-to-50-mph and 50-to-70-mph passing times. Some credit for this specific GLS450鈥檚 extra zip could be attributed to its lack of optional extras, which made it weigh 207 pounds less than that 2015 GL450. A straighter line can be drawn between the new transmission and the GLS450鈥檚 enhanced fuel economy. The two extra gears, both of which are taller than seventh gear in the old transmission, are responsible for nudging the GLS450鈥檚 EPA highway fuel-economy estimate northward by 1 mpg, to 22 mpg.
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