Our cars and trucks are primarily powered through petroleum, a hybrid fuel of petroleum and ethanol, a hybrid combination of petroleum and electric, or diesel fuel; although there is a multitude of other power and fuel sources for cars that are used in America, the primary ones are the ones listed above. The first question to ponder when looking at these fuel sources is to know the overall British thermal unit (BTU) or heat energy for each of these fuels and their numbers are listed in order as follows:
Diesel 138,000 BTU
Petroleum 118,000 BTU
Ethanol 76.000 BTU
Clearly then we can see that diesel is the most efficient of these fuels by a considerable margin. Currently, diesel fuel is priced higher than petroleum but part of the reason is the higher state and excise taxes for diesel fuel as contrasted with petroleum, and further that our refining infrastructure is setup for petroleum which far outsells diesel in the States.
According to the U.S. Dept. of Energy, in 2001, 51.8% of car sales were diesel in the European market which contrasts to the USA in which just 3.2% of auto sales in 2012 were diesel. This doesn't make a lot of sense in which diesel fuel is more efficient, fuel economy is better, and engine life is longer. In almost all cases diesel cars depreciate at a significantly lower rate than petroleum base cars and this fact overcomes their purchase price being initially more expensive. Unfortunately, in America, we have a tendency that when we see the same car such as Volkswagen Golf offered as either a diesel based vehicle or petroleum based vehicle, to notice exclusively that the diesel price of said vehicle is perhaps 10% higher, therefore we instantly conclude that only an idiot would buy the diesel version since the initial cost of the car is higher, gas stations typically devote no more than two pumps to diesel, and the cost of the fuel that runs the car is higher. That is the disadvantage of not actually running all the numbers through which when taken into account factors such as: fuel efficiency which lowers the amount of money that you spend on fuel, depreciation, and upkeep (diesel engines have no spark plugs) clearly shows in most cases that diesel is on an overall cost basis: cheaper. In fact, for the Volkswagen Golf as estimated by bankrate.com the savings over three years and 45,000 miles is approximately $5,013 for the Volkswagen Golf diesel over its gas version.
While the USA spends a considerable amount of time and resources on alternate versions of fuel for cars which run the gamut from vegetable oil to solar to electric, right in front of our noses, is a solution that will increase our fuel efficiency, is well proven, highly available, and can be scaled up in a very short period of time. In the world of diesel v. petroleum, it is the USA that is the outlier. That position needs to and should change.