I have discovered why the price of diesel is now higher than the price of gasoline, when in my youth the reverse was true.

Demand from China and Europe has increased. Refineries in the U.S. have been operating at above 90% capacity over the last ten years. Increasing demand for a fixed supply causes prices to rise in a capitalist system.

The transition to low-sulfur diesel fuel has affected diesel fuel production and distribution costs. In 2006, new EPA standards for sulfur content in diesel fuel started to phase in. By 01-JUN-06, 80% of the on-highway diesel fuel sold in the U.S. had to be Ultra-Low Sulfur Diesel (ULSD) fuel (sulfur content <= 15 ppm), replacing most Low Sulfur Diesel (LSD) fuel (sulfur content <= 500 ppm). By 01-DEC-10, all on-highway diesel fuel must be ULSD fuel. In 2007, new standards for diesel fuels for off-highway consumption started to phase-in. The additional refining has added to the per gallon cost. Cleaner air costs money.

For anyone interested in the data, here are the links.

http://www.eia.doe.gov/bookshelf/brochures/diesel/
http://www.eia.doe.gov/oil_gas/petr...onthly/pmm.html
http://tonto.eia.doe.gov/FTPROOT/pe...mm/03800703.pdf

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Eudaimonia