Weighted average based on sampling of approximately 350 retail outlets, as reported for the week. See (http://www.eia.doe.gov/oil_gas/petroleum/data_publications/wrgp/mogas_home_page.html) for further definitions.
Release: Gasoline and Diesel Fuel Update
US. Energy Information Administration, US Diesel Sales Price [GASDESM], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/GASDESM, May 26, 2016.
FRED BlogParallel prices for oil-based fuels