I believe that the cetane of the fuel varies as well, thus affecting economy...my 300D always bumps between 22-24mpg. But when hurricane Rita came through in 05', all my diesels jumped 2-3 mpg in mileage. I'd read that some red fuel and regular sulfur content fuel had been released into the supply to alleviate shortages. After hearing that, a closer examination of the inline filter on my TD revealed traces of red dye...go figgah.

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Never a dull moment at Berry Hill Farm.