Diesel is coming back to North-America. It was never completely gone, but unless you drove a commercial truck, you had few options. Now, a first wave of diesel models is coming from European car-makers, and a second wave from Asian and North-American companies is expected to follow. What does this mean for us green types?
The pros of diesel are generally recognized to be: Diesel engines are very durable, they are more efficient (you get about 35% more miles per gallon vs. gasoline), they produce lots of torque, and you can generally save on fuel costs (see below for more on that one). They're also able to run on biodiesel (made from waste cooking oil or algae, preferably).The cons: Diesel engines are very durable, which means that very dirty old trucks are still on the road, they generally produce more smog-forming emissions (NOx, PM, etc), they are more expensive than gasoline engines, and they can be noisier and smellier (though recent models have made lots of progress there).
Car-makers have worked very hard to avoid repeating their mistake of the 70s when they first introduced diesel into passenger cars in the US, and many of the cons on the list above have been mitigated. Modern diesels, often called "clean diesels", have improved emissions and many can legally be sold in all 50 US states, including California (though they can't get to SULEV or AT-PZEV ratings). They are also quieter and have better driving characteristics.
So it's all good, right? ~35% better fuel economy, fewer downsides?
Not so fast. The Economist has crunched the numbers and found that if diesel becomes popular in North-America, there will be supply problems and the price of the fuel could rise significantly, erasing any financial benefits over gasoline.
Over the past year, the average price of diesel in America has risen by 117%—twice as fast as petrol. While both carry the same taxes in America, diesel now costs 60 to 70 cents a gallon more than regular gas. [...]
in America, diesel currently costs 20% more per gallon than regular petrol. When that premium reaches 35%, the difference in fuel efficiency will equal the difference in price—and there will be no economic reason to make the switch. Some reckon that day is only a few years away.
So while advanced diesel engines with strict emission controls could help reduce greenhouse gas emissions without contributing too much more than gasoline to air pollution (this would still need work), they might soon be a hard sell to the average person because they won't be financially competitive with gasoline engines anymore. This could seriously slow down clean diesel adoption.
Cirtoën C4 diesel hybrid
Still, our dream transitional car (while we wait for batteries and hypercapacitors to be good enough for electric cars) would be an aerodynamic plug-in diesel-electric series hybrid running on algae-biodiesel and recharged with renewable electricity. With a decent electric range, such a car could be used for weeks without burning a drop of fuel, and during longer trips, it would get very good fuel economy from the small diesel generator.
But that's if you need a car. Otherwise, jump on your bike or take a walk!