Jeep has been making a diesel Jeep Liberty since __.
DaimlerChrysler approves of Biodiesel of up to B5 in the Jeep Liberty and the vehicles are factory filled with B5 Biodiesel.
Dodge has produced some vehicles with Cummins diesel engines for the Canadian market.
Cummins and DaimlerChrysler have recommended that diesel concentrations of up to 5% (B5) should not cause any problems.
For the 2007 model Dodge has approved diesel of up to 20% (B20) for government customers. It is not yet clear if this warranty approval will extend to the general public.
Some background:
http://www.cummins.com/na/pages/en/customerassistance/faq/answers.cfm?uuid=000947AD-64AE-1B8D-BCF080C4A8F00000