Ultra-low-sulfur diesel fuels (ULSD) have been in use for on-road vehicles since last October, when 80 percent of the fuel sold had to be 15 ppm sulfur. The other 20 percent must reach that mark by 2010. Off-highway fuels, on the other hand, dropped to "low-sulfur" from 5,000 ppm sulfur to 500 ppm in June.
The reason for lowering sulfur levels, of course, is to reduce environmentally harmful emissions. But the changeover has sparked apprehension among some fleet professionals. Justified or not, they fear that in solving one problem, others have been created.
Terry Oftedal, senior staff engineer at John Deere, points to several differences between low- and ultra-low-sulfur fuel that form the basis for these apprehensions.
"There is a difference in the energy output of the fuel," he says. "If a fleet manager is used to one type, when he changes to ultra-low he will see a 1- or 2-percent difference in energy content. In other words, his fuel consumption will go up by that amount."
The second difference is in the additives placed in the new fuel to handle lubricity. If you have "old fuel" in the vehicle, or in a storage tank, Oftedal says, debris will accumulate over time in the fuel line and fuel systems. "Because the additive is a natural solvent, it's going to take that sulfur out and you will wind up with plugged filters, at least for the first few tank fulls."
This means that fleet managers will have to change filters on storage tanks; oiling trucks; and, depending on the age of the fleet and how well it has been maintained, on the machines themselves, he says.
"Once you've converted from one type of fuel to the other, storage won't make a difference," says Mark Ensinger, manager of BP's global fuel technology division. "If a fleet manager is using both types of fuel, he has to make sure his storage facilities are isolated from one another. Just a little bit of 500 ppm fuel can go a long way toward contaminating 15 ppm fuel."
A third cause for concern is the impact lower levels of sulfur will have on older machines. "When you start running ultra-low sulfur in those vehicles, you probably will see some seepage in the seals and gaskets," Oftedal says. "The sulfur content is not there anymore to seal it up."
Nor is the lubricity level in the new fuels as high as it was in the old, which could cause problems with rotary injection pumps. "With high-sulfur fuel, lubricity was very high," Oftedal says. With the new ultra-low fuel, lubricity is quite low, so the natural lubricant of the fuel is gone. Rotary pumps, therefore, will wear out faster. It's not something that is going to happen at 100 hours," he said, "but it will reduce pump life."
Few of these concerns have actually materialized, according to Ensinger. "When we went to ultra-low-sulfur fuel with on-highway vehicles, there was a lot of concern about fuel systems not being able to handle it from a lubricity stand point. There were a few problems, but they were few and far between. They washed out as people got used to it.
"Older machines might be susceptible, as far as lubricity is concerned, but the lubricity issue that was a big concern has been managed by added technologies within the fuel," he says. "Lubricity has played out as a non-issue."
On the other hand, newer vehicles will actually work better with ULSD. "The higher the injection pressure, the better spray patterns inside the injectors. All these things have been done to improve the emissions," said Oftedal. "Ultra-low-sulfur fuel helps all these things."
Lubricity concerns haven't become a reality, says Steve Perkins, sales specialist, on-highway diesel engines for International Truck and Engine Co. "I think all the necessary additives are in the fuel. All the 2007 engines, injectors and other components are set up to run on ultra-low-sulfur fuel. All the fuel companies have put in additives to properly lubricate the fuel system, injector pumps and so forth."
International does recommend that customers change the type of oil they are using to a low-ash formula, mainly to reduce soot. "We've gone to low-ash oil mainly because of particulate filters that are required on the '07 engines," he says. "You use a low-ash oil, along with ultra-low-sulfur fuel, and you have less of an opportunity to clog up the particulate filter.
Ultra-low-sulfur diesel also reduces some problems with engine oil itself, according to Oftedal. "That sulfur turns into sulfuric acid, which depletes the additive package in the engine oil. By taking sulfur out, you also help the engine oil by extending engine oil life."
Many managers may have been using the 15 ppm fuel without knowing it, as suppliers may not have enough off-road demand to warrant carrying both the 15- and 500-ppm fuels.
"I know many places won't carry two fuels, so they will carry the 15-ppm sulfur for on-highway and apply it to off-road machines as well," Ensinger says. But, he says, you cannot use the off-road fuel in on-highway vehicles.
In fact, Caterpillar warns cavalier fleet managers who may consider using less expensive off-road fuel in 2007 on-highway engines. For one thing, the company says, it violates EPA regulations and could result in civil penalties. Legalities aside, fuel sulfur levels above 15 ppm can reduce both the efficiency and the durability of the on-highway engine. The potential impact, according to Caterpillar, could be permanent damage to the vehicle's emissions control system, reduced fuel economy and more frequent regeneration events.
"Engine failure resulting from improper fuel usage are not Caterpillar factory defects, and the cost of repair is not covered by a Caterpillar warranty," the company said in a prepared statement.
Although ULSD is expected to cost more, that point is almost moot considering that fuel prices have spiraled through the tent top anyway. "Pricing is what the market is going to set," Ensinger says. "ULSD may have some effect on prices, but it's really about market demand and supply forces."
It is up to International and other OEMs to ease persistent concerns among fleet managers, Perkins says. "[We must] go out and educate our people on proper lubricants and explain to them the differences in ultra-low-sulfur fuel. We all bear that responsibility to the industry, to fleet managers and to our customers."
Oftedal suggests that fleet professionals:
Go to the central fuel source you are using and find out what type of fuel you're actually getting. Have the fuel supplier sample the fuel in your equipment to find out what the sulfur level is. Also, said Oftedal, as with oil-sample kits, fuel-sampling kits are available that can give you the same information.
If you have ultra-low-sulfur fuel, and you've been using it for awhile, you've already passed the problem stage, so relax.
If you are about to enter the problem stage, make sure any PM on fuel tanks and vehicles are "up to snuff." For instance, change filters early on. "The last thing you want to do," said Oftedal, "is experience down time because fuel filters are plugged. And that's probably what will happen," he said.
All in all, Perkins says, "I don't think there really are major issues from ultra-low-sulfur diesel. After all, the Europeans have had it for years." EM