Whereas diesel engines have made great strides in the European auto markets, here in the U.S., gasoline still dominates. Apparently, the prospect of much higher fuel mileage and lower CO2 emissions from diesels doesn't overcome the objections of U.S. environmental regulatory authorities concerned mainly about local air quality issues. I suspect that, even if (when?) these objections are overcome by continued refinement, diesels will still find it difficult to win market share in the U.S., largely because of the wider availability of gasoline.
A possible win-win solution may be forthcoming. A California firm named Transonic Combustion is working on technology that would allow gasoline engines to work at high compression ratios, thus enabling much better energy conversion ratios comparable to what is achieved in the typical diesel engine. Sounds like a great idea to me; hope it works. I wonder, though, if it will provide the throaty sound of those big-block V-8's that Americans seem to love so much.
Richard T. Stuebi is the BP Fellow for Energy and Environmental Advancement at The Cleveland Foundation, and is also the Founder and President of NextWave Energy, Inc.