Uneven Quality Trips Up ’14 Chevy Cruze Clean Turbo Diesel

HELL, MI – How far will the new-for-’14 Chevrolet Cruze Clean Turbo Diesel travel on a single tank of gas? Almost to Hell and back, it appears.

The range question comes with a qualifier, because while the Cruze’s 2.0L 4-cyl. turbodiesel engine performed splendidly otherwise, delivering an average of 42 mpg (5.6 L/100 km) and civilized doses of silky torque, it also failed on the final leg of our test run.

The culprit, according to GM, was a pressurized intake duct becoming disconnected from the throttle body. The result was our pre-production tester sputtering to a stop, stalling, reluctantly restarting and then limping to a nearby service station.

But no big deal, as it turns out.

The auto maker discovered the glitch many weeks before testing in this curiously named hamlet outside of Detroit. It cured the assembly-line hiccup in Lordstown, OH, after building a handful of cars. The engine itself is built in Kaiserslautern, Germany, and draws from a proven architecture dating back 16 years and over millions of European installations.

WardsAuto also tested the Cruze Turbo Diesel on two other occasions, including a salable production model immediately after the engine failure, without incident. So case closed.

Here’s what the Cruze Turbo Diesel delivers without qualification: upwards of an estimated 46 mpg (5.1 L/100 km), making it the most fuel-efficient non-hybrid on the market today; emissions levels 90% cleaner than previous-generation GM diesels, which the engine owes to an advanced exhaust-treatment system; and 264 lb.-ft. (358 Nm) of torque that promises a sprint to 60 mph (97 km/h) in 8.6 seconds.

There’s also a nifty function GM calls “overboost,” where a heavy throttle input will deliver 280 lb.-ft. (380 Nm) of torque for up to 10 seconds. Merging onto a freeway in a small Chevy has never been so dramatic. Or miserly, as it routinely registered instant readouts of more than 50 mpg (4.7 L/km) on the highway.

Standing alongside an idling Cruze Turbo Diesel there’s the familiar “tick-tick” of the high-pressure diesel injectors. Average Americans might find that strange. For others, it could drum up some bad memories of GM diesels that flopped 30 years ago. And then there’s the nagging price premium of diesel fuel, which is averaging about $0.34 per gallon more than gasoline. Not all filling stations carry diesel, either.

Behind the wheel at cruising speeds during testing here, the environment inside the Cruze Turbo Diesel differs little from its gasoline cousin. A host of sound attenuation items meant to eliminate, block or absorb unwanted noises performs well, and a sixth gear running at a relatively low 2,500 rpm further quiets the cabin at highway speeds.

Subsequent testing in another Cruze Turbo Diesel model delivers remarkably different results. Noise and vibration permeate the cabin, telegraphing through the steering column, gear shifter and arm rests.

The engine itself receives a number of changes to homologate it for the U.S. market, including an aluminum intake manifold that improves combustion, ceramic glow plugs and an auxiliary oil-pan heater for better cold-start performance and a new timing belt and tensioner for longer life.

The engine retains its iron block to handle the higher cylinder pressures of a diesel, and GM replaces an in-house gearbox with an Aisin 6-speed automatic transmission also for durability reasons. The Aisin fits in nicely, providing smooth shifts and none of the busy work normally accompanying a 4-cyl. engine.

GM adds some aerodynamics tricks from the Cruze Eco model, such as active aero shutters in the front grille and improved underbody treatment to make the diesel model slippery enough to reach an estimated peak 46 mpg. That’s better than the 42 mpg (5.6 L/100 km) delivered by the Volkswagen Jetta TDI, its primary competitor.

GM says the Cruze Turbo Diesel will travel as far as 717 miles (1,154 km) on its 15.6-gallon (59.0 L) fuel tank, or just a few miles shy of a Detroit-to-Boston road trip. One GM engineer boasted of squeezing 900 miles (1,448 km) from a single fill-up by driving 5 mph (8 km/h) below the speed limit on a cross-country trip.

But arguably the big knock on diesel, at least the previous-generation technology, has been its dirty emissions. The exhaust smell, and its fuel for that matter, also was a turnoff. And in the U.S. and Canada emissions laws are more stringent than those in Europe; California’s are even tougher.

So GM adds a complex exhaust-gas-recirculation system with a high-capacity cooler and bypass feature to lower combustion temperature and thereby reduce emissions of nasty nitrogen oxide. An exhaust aftertreatment system, including a diesel particulate filter and urea-fluid injection, further reduces NOx emissions.

No, the Jetta does not carry a similar system, but expect the addition in ’14 to meet tightened U.S. standards. The larger ’13 Passat TDI already uses a urea aftertreatment system.

It’s also worth noting the Cruze Turbo Diesel costs $2,600 more than a base diesel Jetta outfitted with a 6-speed manual transmission.

But the Cruze Turbo Diesel comes better-equipped from the factory with items such as OnStar, turn-by-turn navigation, leather-trimmed 6-way power front seats, four additional airbags and other safety items including a rearview camera, side blindspot and rear cross-traffic alert, daytime running lamps and rear park assist.

Jump up to a comparably equipped Jetta TDI with a 6-speed automatic and the sticker can eclipse that of the Cruze Turbo Diesel.

At the same time, the lack of manual transmission could be a soft spot for the Cruze on the showroom floor. Americans greatly prefer automatics over manual gearboxes, but the diesel niche contains some peculiar characters who like rowing through the gears themselves.

In the end, the Cruze Turbo Diesel proves itself a capable competitor to the Jetta, which has owned the small but profitable segment for a number of years. If GM irons out the hiccups, it could develop a cult following for the car. Let’s hope they do, because diesel’s time in the U.S. is now, and the technology can’t afford to come with qualifications.

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