Diesel cars average 25 to 30 percent better fuel economy than comparable gasoline models, but the diesel is more expensive. At the beginning of July, 2008, the national average for a gallon of diesel was $4.70, versus $4.06 for a gallon of unleaded regular gasoline, according to the Energy Information Administration.
There are a couple of reasons for this: limited demand here in the States, and subsidies in foreign countries that increase demand for diesel internationally.
Avoiding the Fuel Pump
Electric cars require no gasoline, but buyers need to install recharging devices at home. The other limitation is driving range, which is shorter than for gasoline cars. The new Chevy Volt has a range of 64 kilometers: about 40 miles.
Engineers plan to introduce an on-board generator to recharge the Volt's battery pack on the go: no word yet as to whether that generator will be standard equipment on the car.
Fitting Technology to the Driver
Having mentioned some hidden costs in going green, the question remains: is there any cost benefit? The answer is 'yes', if the driver chooses technology according to his needs.
Hybrid cars are most beneficial for people who drive in crowded urban areas. On most hybrids, the gasoline engine shuts off at idle while electric motors run the accessories. Some hybrids can also run on electric power at low speeds: the Chevy Tahoe and Dodge Durango hybrids are two examples.
Hybrid fuel economy in stop-and-go driving is significantly better than for gasoline cars. The Toyota Highlander Hybrid averages 27 miles-per-gallon in the city, as compared to 18 miles-per-gallon for the gasoline model. The Toyota Camry Hybrid gets 33 miles-per-gallon in the city, compared to 21 mpg for the four-cylinder gas car, and 19 mpg for the V6.
While these cars also get excellent fuel economy on the highway, the advantage over gasoline models is not as significant. The exception is the Toyota Prius: it averages 45 miles-per-gallon on the highway, and has better overall fuel economy than any other Toyota model.