Mazda is pushing ahead with its plans to offer a clean-diesel four-cylinder engine that could prove to be a strong rival to the TDI four in some Volkswagen and Audi products.

While the 2014 Mazda6 will arrive in its lower-priced form with a 184-horsepower, 2.5-liter version of the four-cylinder engine, the automaker confirmed at the Los Angeles Auto Show this week that a 2.2-liter four-cylinder diesel engine will be available this next year—and like the gasoline engine, it will be offered with a choice between six-speed manual or six-speed automatic transmissions.

Both engines, termed SkyActiv-G (formerly called Sky-G) for the gasoline engine and SkyActiv-D (or Sky-D) for the diesel, fall under the automaker's SkyActiv engineering initiative, focusing on developing a core suite of powertrain and weight-reduction technologies aimed at reducing emissions and fuel consumption without cutting into driving fun, and reducing vehicle weight without detracting from safety.

Last year we drove a special Mazda6 mule equipped with the Sky-D engine and found it to be very quick and surprisingly refined—surprisingly so because diesel engines have in the past been loud and clattery as well as rough-running at times. The Sky-D, on the other hand, felt like it could potentially be installed in a luxury model.

Mazda SKY-D Engine

Mazda SKY-D Engine

Mazda hasn't released formal specs for gas mileage or even power output yet for the U.S. version, although the version we tested made about 170 horsepower and an extremely impressive 310 pound-feet of torque. Mazda had previously said that the Sky-D goes about 20 percent farther on a gallon of gas than a comparably sized gasoline engine, so it wouldn't surprise us if this engine earned numbers in the upper 20s in the city and more than 40 mpg on the highway.

On the emissions front, the engine doesn't need urea injection to meet U.S. Tier 2 Bin 5 emissions requirements. Its very low (for a diesel) 14-to-1 compression ratio is one of the keys to that; although it does have a large oxidation catalyst and a particulate filter system.

But the clean-diesel isn't the only piece of useful green technology to make it into the U.S.-market Mazda6. It will also be the first production model to get Mazda's i-ELOOP system, a capacitor-based regenerative braking system that can more quickly capture the energy in braking and release it to help supplement the power demands of accessories or air conditioning—increasing fuel efficiency but with far less added bulk than battery packs.

The i-ELOOP system is combined with engine start-stop functions—although Mazda didn't verify this aspect at the conference or in the coordinated release.

Gasoline versions of the 2014 Mazda6 is due to begin reaching dealerships in January 2013, while the diesel model will go on sale in the spring.


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