Why is diesel fuel so much more expensive than gasoline?

Every teenage kid has to have a diesel truck chip to give it more horsepower,throw the black smoke out the exhaust to show off.at least in this part of the country.

Absolutely not a factor. The vast majority of diesel is burned by people who make a living with it. Heavy trucks, tractor trailers, farm tractors, trains ect. Diesel is much more forgiving demand wise when prices rise because these people need it regardless of price. So there is less pressure on fuel companies to keep the price low. Gasoline will see loss of demand when prices rise as people combine trips and reduce unnecessary travel. This is of course just my opinion on the situation. I could be wrong, but I doubt it.

Im not sure but it sucks. When I had a gas burner diesel was cheaper. As soon as I got a diesel they shoot up past gas in cost per gallon.

If i remember hearing right, some old timers talking how diesel is almost a by product of refining gas. They said back in the 70's they use to burn off the diesel as they had so much of it after the refinery process. They also said other than gouging, its one of the biggest money makers the petroleum industry has.
Also it sucks when the gas stations raise the prices before they get a new delivery.

Highway taxes are greater on Diesel. The assumption is that large Diesel trucks cause more wear and rear on our highways, so they should pay more highway taxes at the pump.