In the last few months fuel companies started rolling out a new ultra low sulfur diesel fuel (ULSD). This new EPA mandated fuel has cleaner emissions than the prior low sulfur products that have been sold in the past, but with a trade off of less lubrication and lower cetane. Current diesel engines should run without any trouble on the new fuel, however you can extend the life of your engine by using a fuel additive that replaces these lost fuel components. Messicks recomends the FPPF "Total Power" Fuel Treatment for most heavy equipment engines.
FPPF Total Power Fuel Treatment