Diesel engines boost small car efficiency

Catering to mileage-conscious American shoppers, car companies are starting to equip more of their U.S. offerings with extra-efficient diesel engines. Diesels already enjoy substantial market shares outside the United States, but over here consumers have yet to adopt oil burners en masse. After developing a new generation of powerful and refined diesels, many automakers are hopeful that U.S. customers will reconsider.

2014 BMW 320d

Shoppers may be familiar with the higher mileage that diesels achieve through efficient combustion and use of a fuel that packs more energy into each gallon. To see how these efficiencies translate into overall environmental friendliness, we’ve rated a sample of the new diesels with the comprehensive AutoEcoRating system.

The BMW 320d, VW Jetta TDI and Chevy Cruze Diesel each earn scores that fall within six points of one another. The BMW 320d ranks highest with an eRating of 128, reflecting its highest combined mileage of 37 mpg. As a point of comparison, this year BMW also introduced a new, efficiency-tuned version of the gasoline-powered 3 Series, designated the 320i. The 320d bests the 320i by 31% in terms of fuel economy and provides a 6% decrease in total pollution per mile.

Volkswagen’s Jetta TDI, with an eRating of 125, similarly improves upon the mileage and eRating of the gasoline Jetta SE engine.

Conversely, the Chevy Cruze Diesel was outscored by its gasoline-powered counterpart. The diesel Cruze earns an eRating of 122 while the gasoline Cruze earns an eRating of 146.  In this case, Chevy’s gasoline engine with its added ultra-clean catalytic converter controls smog-forming pollution from the tailpipe far better than any diesel system can do today, in spite of the fact that the diesel burns less fuel per mile.

While boasting impressive fuel economy — especially on the highway — these diesel powertrains come at a cost. The move from a comparable gasoline model can add as much as $6,000 to the sticker in the case of the BMW. Even with the higher price, manufacturers are optimistic that a growing number of buyers will find appeal in the diesel’s unique combination of power and efficiency.

Make and Model$MSRPSpecsMPG (City / Hwy / Comb)eRating
BMW 328d39,5252.0 L 180 hp 4 cyl. diesel,
8-speed auto
32 / 45 / 37128
VW Jetta TDI24,9502.0 L 140 hp 4 cyl. diesel,
6-speed auto
30 / 42 / 34125
Chevrolet Cruze Diesel25,6952.0 L 151 hp 4 cyl. diesel,
6-speed auto
27 / 46 / 33122

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