Diesels are a good thing, but there are downside items as well. To treat diesel as the solution for ALL cars would be extremely shortsighted. No fuel should again become a monopoloy as gasoline has - we need to learn that lesson well.
Some of the negatives are:
-Diesel is already more expensive than gasoline
-Diesel is not easy to find (trust me, I drive one everyday)
-Diesel is much more difficult to bring into emissions compliance
-Diesel is a petroleum product, and would not solve the supply problem nor dent our importation of oil enough to matter.
-Biodiesel has a host of issues when being used in modern diesel engines from incompatibility with the mechanicals to the tendency to solidify(especially in colder weather). B5 (5% bio/95% petro diesel) can run in most engines and B20 can work in many engines. Beyond those relatively low percentages, the problems become much more significant - especially as you approach B100 (vegetable oil). Technology is progessing on these issues but has an uncertain future at this point.
- Manfacturers generally do not build diesel engines to be compatible with biodiesel.
So while beneficial, and having an important role in our future fuel supply, biodiesel is far behind e-85 as an immeditely viable alternative.
As has been pointed out above, American consumer perception of diesels is less than positive (though largely incorrect). This also will temper the automakers' willingness to bring them to market here.
And SMK, your information on ethanol is outdated and flawed - get caught up.