Volkswagen CrossBlue Concept

At the Detroit Auto Show, Volkswagen showed not just one but two concepts with diesel plug-in hybrid powertrains. VW not only unveiled its CrossBlue Concept for a mid-size seven-passenger crossover, it also showed the CrossCoupe Concept it had premiered last year at the Beijing Auto Show. Each vehicle uses a diesel-electric powertrain, which in the CrossBlue is rated at 306 horsepower combined. Together, the turbodiesel engine and electric motors together put out a whopping 516 lb-ft of torque when all four wheels are powered. But one factor that seems to have escaped notice is that the...