Only 40% of a barrel of crude oil can be made into gasoline. The rest of the oil can be distilled into diesel/heating oil, heavy gas oil, lube oil, kerosene, naptha, and light gas. Diesel used to be substantially cheaper than gasoline, but increased use of tractor-trailers and train engines, which all run on diesel, has strained the available supply. Refineries can either optimize for gasoline or diesel production. Gasoline is a better profit center right now as the high-end production equipment that was installed about 10 years ago is finally turning in big profits. Refiners would have to invest billions to retrofit an existing gasoline line or build a diesel refinery and they will not do that as the short-term profit to investors would be at risk.

The primary reason diesel sells for a different price than regular gasoline is taxes. Gasoline is taxed at the point of use: the gas pump. Diesel is taxed differently depending on where you buy it, considering that many commerical trucks use diesel. Take note the next time you see a semi driving down the road to see the license plate. It may read - apportioned. What this means is the fuel taxes are equally apportioned according to the use of the vehicle across state lines. As you can guess, fuel taxes vary from state to state, so accordingly, diesel fuel prices will find a median value at the pump due to the fact that they are primarily regulated and sold with commercial use in mind. It makes no difference that you might buy it to put in your diesel vokswagen. Another reason diesel prices are different is that the fuel is not as costly to refine than gasoline due to the fact that it isn't as heavily regulated regarding pollution standards.

Today, 4-22-06, the prices are equal. two gas stations had the same identical price for diesel as regular unleaded. i agree with the other two answers, they both are correct. the bottom line is this, there are many more gasoline-fueled automobile engines, rather than diesel. and, for what its worth, today that does not mean anything. a barrel of light crude oil has hit a worlds record and no end in sight. $75.00 a barrel! tomorrow, it may hit $100.00 a barrel. Being everything equal in the world, its a very good bet that diesel fuel will equal the price of regular unleaded gasoline, from this day forward. have you noticed the number of tractor/trailer rigs, on the side of the road, out of fuel? this is not a good sign. I realize truckers pull to the side of the road, when its sleep time. i am referring to the big rigs that run out of fuel, mostly independent drivers. 2 or 3 times a day, i call a service truck for tractor/trailers that are out of fuel......empty and sometimes block traffic.

I saw diesel down the road from where I live today 18/05/2008 at $1.679/litre and regular unleaded was $1.379/litre. As a truck driver here in Australia, I can only imagine what this would do to the economy worldwide if all the trucks around the world simultaneously stopped working for a week. Could you imagine the whinging and complaints from all the politicians and the big oil company executives when they couldn't buy their bread or milk from the supermarket, because there were no trucks to deliver it? What if they couldn't get their weekly fix of alcohol or cigarettes, because trucks couldn't deliver it. What if the steel trucks stopped delivering steel to building sites and car manufacturers, what would happen to our global economy? What do you think delivers everything in this world environment that is consumed by humans? The pedal power of bikes, maybe we could have skateboard couriers!! Everything that is delivered to a supermarket or corner shop for our own conveniences has somehow and somewhere been first delivered in a truck. If you look at all the long distance line haul trucks in Australia that drive anywhere up to 6000 kilometres a week and beyond, some of these trucks are only getting 1.5km/ltr. Just do the maths on that and their weekly fuel bill for 6000km/week would be $6400.00 approximately. Where is the justification in that when only about 2 years ago we were looking at $2800.00/week approximately? With the housing crisis worldwide, and the diesel pricing going stupid because the oil companies & governments want to make a quick buck, what will become of the worldwide homeless rate of families being sold up because they can't make payments on their house and/or trucks, their livelihoods’??? The governments & oil company tycoons in this world stage of today need to sit back and look at the bigger picture here. If diesel is based on supply & demand, what would happen to the price of diesel if no diesel was bought worldwide for 1 week? It would be catastrophic to the economy! Governments & oil companies need to pull your heads in otherwise you will drive trucks out of the market with your ridiculous profit making and everybody will be worse off.