If one really wants to understand what's going on in the gasoline versus diesel market, I'd suggest reading
THIS ARTICLE that appeared in today's (Dec 30th) edition of the Houston Chronicle. An excerpt:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">A drop of more than $100 a barrel in oil prices in recent months has lowered regular gasoline prices, but global demand and tighter supplies have kept diesel prices high. </div></BLOCKQUOTE>
Rusty