You are probably right here - I have been seeing the spread between diesel and RUL growing in recent days.  Right now diesel is $3.19 - RUL is $2.79.

I hear rumors that the introduction of ULSD will be delayed, but nobody can find out anything concrete.  I have a friend who is a reporter for a trade rag for truckers, and she was getting quite frustrated with the EPA because she couldn't get a straight answer about this from them.

The problem is the EPA has new regulations for heavy truck emissions coming online for the 2007 model year (which means May 2006). The Particulate filters and catalysts for the 07 engines require ULSD or else they will be fouled. At this point there is not any certainty to what happens to the warranty for one of these engines ($15k+) if non ULSD is used in it.

SO to bail on the ULSD requirement would also require bailing on truck emissions (after 5 years of R&D and the start of a changeover in production). Even if the new requirements go forward mixed availability of ULSD would be another reason for fleets to hold off on the new technology (already there is a massive pre buy going on with fleets loading up on new trucks this year so they do not have to buy new trucks until the tech is proven for a year or two)