File this under the heading: You Knew It Was Bound to Happen.

U.S. Environmental Protection Agency rules require that ultra-low-sulfur diesel fuel be available everywhere in the U.S. by Oct. 15. Specifically, the rules say that 80 percent of diesel sold for highway use after Oct. 15 must have no more than 15 parts per million of sulfur.

So, two weeks before that official deadline, unforeseen or unintended consequences of the changeover are beginning to pop up and they could drive the price of ultra-low-sulfur diesel higher than had been predicted.

A couple of examples:

Each winter, kerosene-based No. 1 fuel is blended with No. 2 diesel to make the No. 2 diesel flow better in cold weather. However, this winter, theres expected to be a shortage of ultra-low-sulfur kerosene that can be mixed with the ultra-low-sulfur diesel fuel. And you know what happens when there is a shortage of anything, the price goes up and/or there is limited availability.

In the coldest areas where the kerosene blending is common, if the shortage is severe enough, bus and truck operators may be forced to use cold- flow improver additives, which are expensive and sometimes in short supply.

The basic problem, according to one oil company executive, is that a number of refiners will choose to abandon the No. 1 kerosene market this year rather than spend a lot of money to produce kerosene components that have sulfur levels low enough to be mixed with ultra-low-sulfur diesel for on-highway use.

If you operate in a cold climate, now may be a good time to talk to your fuel supplier.

Unforeseen consequence No. 2: Trucking executives say there is a good chance there will be a shortage of tank truck capacity in the coming months, as demand for ultra-low-sulfur-diesel fuel, ethanol and biodiesel grows.

Increased transport of ethanol and biodiesel from plants to terminals - and the unresolved question of whether to dedicate trucks to the transport of ultra-low-sulfur-diesel fuel - could tighten an already strained fuel transportation market, according to tank truck executives.

"ULSD and ethanol [are] driving up demand for tank trucks," one petroleum hauler told an online news service. "That places an incredible demand on an already tight industry, and that means prices for fuel may go up as a result of that tight market."

Enough questions have been raised about the situation that the Government Accountability Office is going to study the nations renewable-fuel infrastructure.

One possible solution that is likely to be proposed is to grant fuel haulers a waiver on driver hours-of-service rules. That happened last year during the Gulf Coast hurricanes and again in mid-July, when the governor of Nebraska issued a waiver of hours-of-service rules to help assure there was enough fuel during the summer harvest season.