Diesel Hybrids
I’ve been wondering for a couple of years why we aren’t seeing diesel hybrids. America is definitely more of a gasoline economy than a diesel one, so I understood why we saw gas hybrids first. With the popularity among the green set of biodiesel, it seemed to me like there might be a stronger than expected demand for hybrid diesels that could be converted or built from scratch to run biodiesel. Diesel is already more fuel efficient than gasoline engines. Combine that with a hybrid, with the new, cleaner diesel or biodiesel, and you’ve got a green star in the auto market. It looks like they may not be too far off, at least in Europe. GM is introducing a 60mpg concept hybrid diesel version of its Opel Astra sedan. A version of the current production Astra is headed to the US later this year as a Saturn. DaimlerCerebrus is working on hybrid diesels both for its Mercedes car and Dodge Ram truck lines.
June 9th, 2007 at 12:47 pm
Diesel represents a big controversy from an environmental standpoint. Diesels have lower specific fuel consumption than petrol engines and produce fewer unburnt hydrocarbons, CO, and CO2, but because of the nature of diesel combustion, which is inherently ‘lean’ and higher-temperature than gasoline engines, they have significantly higher NOx emissions. Euro emissions standards — up until next year, I think — have had separate tiers for petrol and diesel, although that’s a matter of great controversy in the EU. It is possible to make diesels meet U.S. federal NOx standards, but it’s expensive, requiring complex NOx catalysts. Such catalysts are also incompatible with the high sulfur content that U.S. gasoline has had (which also kept us from getting technologies like direct-injection). Low-sulfur fuels are now being phased in here, and so Mercedes is about to roll out its “Bluetech” diesels for the U.S. market. I think they will still not be available in states with California-style emissions, making them 44-state vehicles.
Hybrid or not, I would buy a BMW 330d if I could. It has superb real-world performance (no top end, and a somewhat heavier nose, but boatloads of torque), and in the kind of driving I do, I would get around 30% better fuel economy than I do with the Mazda. (I generally get 25-28 mpg overall, topping 30 only in steady highway driving, whereas the 330d would drop below 30 only if I spent all my time on the drag strip.)