Why doesn't the government cite the big oil companies for price gouging for the highly inflated diesel prices?

Diesel costs far less than gasoline to refine, so logicaly it should be lower in price. In fact it was during the eighties, I drove an oil tanker for a small fuel oil company and diesel fuel was about twenty cents cheaper per gallon, now it's about eighty cents more per gallon. I know that the cost of refining it is still lower than gasoline. aren't there laws against price gouging on the national scale?