Reply #3: Two reasons

[tammywammy]

it's winter, and the cost of heating fuel increases.

2. The refineries had to reformulate diesel to meet new EPA restrictions, thus more cost for the per gallon price of diesel. My uncle who works at a refinery said (this was back in late Sept) they expected the price to increase $0.50 per gallon because of the reformulation. They were getting ready to change over to the reformulated diesel when Rita hit.

For what its worth, I drive a diesel Beetle, and even with the higher cost, I wouldn't trade it, because the mpg is much better. It's still cost beneficial to run diesel vs gas.