Yes, it is mostly a US problem. My professors were constantly *****ing about how they can't use diesel engines effectively here because the fuel itself has so much sulfur in it that any kind of catalytic converters get poisoned to the point where they are useless almost immediately. Cleaner diesel standards were recently passed, but IIRC, they still aren't up to European standards which have been around for quite some time.
BTW, unless I misunderstand you, "particulate filters" don't have any effect on the emissions I'm talking about. Soot emissions are an entirely different phenomenon and much easier to address than NOx emissions (which are responsible for the lovely yellow haze you see hovering over major cities these days).
Also, the efficiency improvements gained by a diesel engine are hindered by the fact that the engine has to be significantly heavier. Higher compression ratio --> higher loads --> additional strength required --> heavier. I'm not disagreeing with you, though. A diesel car should be more fuel efficient than a gasoline car, but I question Ashrak's notion that a diesel car is more fuel efficient than a gasoline hybrid car. Unfortunately, I'm not aware of a vehicle that comes in gasoline, diesel, and hybrid trims for direct comparison. I'd certainly be interested in a diesel Civic.
