Nearly three months ago the explosion of BP’s Deepwater Horizon oil rig unleashed a monumental environmental disaster on the Gulf of Mexico and beyond. But you’d never know it by checking out the price at the pump for diesel fuel over the last two months or so. Nor would you think the economy is picking up steam when you do a double-take at the still-falling price per gallon of highway diesel.

According to the Dept. of Energy’s latest Energy Information Administration (EIA) Weekly Retail On-Highway Diesel Prices report, as of July 12th the average diesel price was $2.903-- down 21 cents from the $2.924 posted the week before. And since the May 17th EIA report, the national average price has dropped each week.

Oil is slippery stuff, so perhaps it should not be surprising that analysts might have differing takes on why diesel fuel prices keep sliding down-- especially when factoring in the realities of today’s global economy.

“Diesel prices follow a simple supply-and- demand equation,” analyst Noel Perry , principal of Transport Fundamentals and managing director & senior consultant with FTR Associates, told FleetOwner. “Because of the recession, worldwide demand for crude is relatively low and there is a mild surplus of OPEC capacity. Until that surplus is consumed by growing demand prices will remain ‘low’. Second, U.S. refining capacity is working at full tilt with no major outages. That keeps the refiners’ markups low

“Truckers will enjoy such prices until the world market heats up, probably in 2011,” he continued. “If we have an aborted recovery – which is unlikely-- it could be several years. “ Perry added that “any effect of the new [federal] drilling moratorium will be delayed – as the market gets reduced access to new supply. “

“Diesel doesn’t necessarily have the seasonality that gasoline has,” Denton Cinquegrana, senior markets editor, Oil Price information Service (OPIS), told FleetOwner.”But diesel prices, and to a lesser extent, gasoline prices, have been coming in at the retail level some weeks with pretty small drops, but drops none the less. As far as oil prices --and with that diesel and gasoline-- are concerned, the market peaked in early May, not necessarily too far off from normal peaks”

Cinquegrana advised that while May saw prices jump, June and July “were pulling back and a bit stagnant—they would move up some then come back…. [I] have a feeling that August may be pretty sloppy. A hurricane or some other unforeseen circumstance can change that, though. “Demand right now just really isn’t there like you would think,” he added. “Yet refiners are operating at a pretty high rate. Last week DOE said refiners operated at 90.5% of capacity, which is a high for 2010.”

Both Perry and Cinquegrana are not surprised that the BP disaster has not moved oil prices. “The gulf disaster is a drop in the bucket as total supply goes,” noted Perry. Cinquegrana said it is “more of an environmental disaster than an oil supply disaster. With that said, I don’t think there will be much impact from the spill, pricewise at least, until the middle of this decade.”

However, analyst Chris Brady, president of Commercial Motor Vehicle Consulting (CMVC) and a FleetOwner columnist, pointed up the impact that another disaster—the global financial meltdown— is having on oil prices. “When the financial crisis, started, institutions began buying oil as a hedge against the U.S. dollar,” he explained. “[That’s because] when the dollar depreciates, the price of oil rises. But then came the financial meltdown in Europe, driven by the debt crisis that hit such countries as Greece and Portugal. That in turn drove down the Euro and drove up the U.S. dollar. And that has brought down the price of oil.”

Brady said the upshot is oil is now “trading like a financial instrument, rather than being driven by supply and demand. And when it gets back to being controlled by supply and demand is anyone’s guess.”

OPIS’ Cinquegrana concurs. “Right now, oil and refined products appear to be following the direction of the equities markets,” he said. “NYMEX futures have become more of a financial instrument for Wall Street over the last couple of years, more so than a place for refiners, end users, etc. to hedge their costs. So if the economy is looking a bit shaky oil tends to fall off. It has become somewhat disconnected from its fundamentals.

“There is still plenty of oil in storage, gasoline and diesel too,” Cinquegrana continued. “Demand has been sputtering of late. We saw a jump in gasoline demand ahead of 4th of July holiday—that’s not really a surprise-- but gasoline demand has come off a little bit more than we expected. Diesel demand, when you compare it to last year, looks like it is growing in leaps and bounds. However, that view should be taken with a grain of salt-- as last year at this time we were scraping the bottom for diesel demand.”

“What has happened,” CMVC’s Brady added, ‘is that lower crude prices have filtered down to the fuel pump.”