the impact of biodiesel on emissions warranty, in-use liability, and antitampering provisions;

the impact of long-term use of biodiesel on engine operations;

the options for optimizing these technologies for both emissions and performance when switching between biodiesel and diesel fuel; and

the impact of using biodiesel in these fueling systems and engines when used as a blend with 2006 Environmental Protection Agency-mandated diesel fuel containing a maximum of 15-parts-per-million sulfur content.