The problems were at least partially due to the transition to ultra low sulfur diesel fuel, mandated by the federal government in conjunction with the 2007 diesel engine emissions standards. ULSD also may be more likely to have water issues, which is a greater danger than ever with today's engines and also could mean increased microbial growth.

Cold Shoulder

          Most of the problems stemmed from the colder-than-expected conditions, according to Rich Moskowitz, regulatory affairs counsel with the American Trucking Associations. He says fuel terminals had not properly additized the fuel to perform in that kind of severe weather. "Once the terminals recognized what they were dealing with and used the appropriate additive package, those problems seemed to dissipate."

          The U.S. Environmental Protection Agency told ATA the gelling problems were not directly related to the chemistry of ULSD, but admitted that some batches of ULSD may be difficult to winterize with existing cold-flow additives.

          "We tend to think that ultra low sulfur diesel is all the same," says Tom Weyenberg, business manager for diesel fuel additives at Lubrizol, which makes additives used by fuel refiners. "Actually, each refinery's ULSD is a little different. It all depends on the crude oil that they may be starting with, and on the processing, how they actually get down to ultra low sulfur. Some are very easy to treat; some are much more severe." In many cases, additive makers had not had a chance to get their cold-flow additives optimized for these many different variations on ULSD before winter hit.

          Some experts disagree with the EPA's stance and believe there are indeed differences in the chemistry of ULSD that affect how additives work.

          Cold-flow additives normally work by affecting the formation of wax crystals. When you change the fuel, you change the chemical process of how wax crystals form. Since the fuel is different, the additives need to be different as well.

          Gary Pipenger, president of Amalgamated Inc., a fuel additive supplier in Fort Wayne, Ind., says many of the new ULSD fuels produced in North America had fuel cloud points that were 5 to 7 degrees higher than in previous diesel fuels. One of the reasons, he says, is the significant reduction in aromatic content associated with the new fuels – about a third less, thanks to the hydrotreating and other sulfur reduction methods. The lower aromatic content, he says, reduces the natural tendency of solidified paraffin wax to stay suspended in the liquid fuel for a few degrees of temperature drop below the cloud point. It also makes the paraffin more likely to bond with any moisture in the fuel, making it heavier and likely to drop to the bottom of the tank, where it's pulled into the fuel pump and clogs the filter.

          Another problem was the lack of No. 1 diesel (often referred to as kerosene) available to create cold-weather blends, which has been a standard procedure for trucks operating in northern states in the winter. In order to legally produce such a blend with ULSD, the No. 1 now has to be ultra low sulfur as well. And ultra-low sulfur No. 1 diesel was either not available at all last winter, or priced too high.

          Some fleets that were able to get the No. 1 fuel still had issues. On the other hand, some fleets didn't do anything special or different this winter and had no significant problems.

          Many of these issues will likely have improved by this winter. Additive makers have been working on revamping their formulas, refineries may be making some changes at the refinery level, and experts predict more availability of ultra low sulfur kerosene.

Water, water everywhere

          Water in ULSD may be another potential problem. While water has always been a common component of diesel fuel, some say it acts differently in ULSD, in ways that can cause greater problems in the engine and increased free water in storage tanks.

          Water is an issue for two reasons: It's hell on injectors, and it harbors microbes.

          Today's low-emissions diesel engines are using higher pressures and tighter tolerances. The small moving parts within an injector nozzle used to have clearances in the thousandths of an inch. Now we're talking 3 to 5 microns. With those kinds of pressures and tight space, water in the fuel can damage injectors.

          The second issue with water is microbe growth. A number of industry experts believe USLD may be more likely to grow microbes in storage. Microbes like to proliferate where the water and fuel meet in a fuel storage tank. Making matters worse is that sulfur, a natural biocide, is no longer present in enough quantity to perform that function.

What You Can Do

          To help protect yourself this winter, do your homework. Talk to cold-flow fuel additive suppliers about whether their additive is optimized for ULSD in the areas where you regularly run. Buy winter-blended fuel when appropriate. If you run in the northern states, consider adding fuel-heating equipment to your trucks.

          To avoid injector damage from water in the fuel, fuel/water separators may be more important than ever. If you don't have one, consider investing in one. If you do have one, make sure you drain the water out regularly.

          Carry fuel filters with you in case of plugging problems, whether from fuel waxing in cold weather or microbial contamination in warmer temperatures.