Introducing a new fuel into the fleet does not come without consequences—especially for maintenance. But, will the anticipated cons of higher fuel prices, lower lubricity, and lower energy output outweigh the projected pros of cleaner emissions and improved air quality once Ultra-Low Sulfur Diesel (ULSD)-fueled vehicles begin regular maintenance schedules?


From January 1, 2007, all Y2007 and later model year diesel highway vehicles are required to use Ultra-Low Sulfur (S-15) Diesel fuel. California mandated use of ULSD for all diesel highway vehicles as of September 2006.

Vehicles that require ULSD fuel have specific labels on the dashboard and near the fuel inlet indicating that they must be fueled with ULSD fuel. Vehicles without these labels may be refueled with either Low Sulfur Diesel (LSD) or ULSD fuel.

Patrick Kelly, downstream associate with American Petroleum Institute (API) in Washington, D.C., explains that the U.S.

Environmental Protection Agency (EPA) sought input from the engine and fuel industries regarding sulfur levels with the new ULSD. Auto and engine makers wanted a limit of 10 parts per million (ppm), but the oil industry felt that 50ppm was sufficient for the kind of advanced emission control systems that the industry was likely to use. He says EPA probably chose 15ppm, based on NOx absorbers that require the lowest sulfur ppm level.

An FYI to fleets during conversion to ULSD is that it may be necessary to develop a method for measuring sulfur content in bulk storage.


Darry Stuart, President of DWS Fleet Management in Wrentham, MA, and current chairman of the Technology & Maintenance Council (TMC), says the main issues causing ULSD "petro-noia" in fleet maintenance are fuel prices, availability, cold weather operation, lower lubricity, performance, and equipment and consumables expenditures.

EPA previously estimated that ULSD would cost an extra five cents per gallon. The Energy Information Administration (EIA), which provides official energy statistics from the U.S. government, believes that number is actually between five and eight cents per gallon.

According to EPA, ULSD fuel costs more to refine and distribute than Low Sulfur Diesel fuel, but many factors affect the consumer price of fuels, including the price of crude oil, geopolitical factors, weather, transportation and economic events, as well as supply and demand.

Tom Komos, vice president of fuel supply and marketing for TravelCenters of America (TA), offers that ULSD costs more to refine. He adds that some customers are "…wary of potential cost increases for a product that many do not yet need."

TA's vice president of sales, Mike Lombardi notes, "Some fleets had to revise their billing/payables systems to add a second type of diesel fuel. TA has partnered with several fleets to assist in converting their pricing and payables systems to handle two types of diesel pricing."

Bob Pudlewski, chairperson for the technical committee of the National School Transportation Association (NSTA), headquartered in Alexandria, VA, says price increases vary across the country. "Generally, we are seeing five to 10 cents per gallon difference," he says.


"The biggest concern is availability," says API's Kelly. "Refiners are required to produce 80 percent that will be ULSD. They are over-complying by producing about 2.6 million barrels a day, which is over 90 percent needed for U.S. highway vehicles."

TA's Komos explains that ULSD can be downgraded as it moves through the supply system to account for real product degradation. "These downgrades are limited to 20 percent of the ULSD handled at each step of the process (pipelines, terminals, delivery and retail). Downgrade restrictions ensure that ULSD will be available at retail outlets for trucks that require it," he says. "Most customers prefer the old product, LSD, as it tends to be a little cheaper and the drivers and trucking companies are most familiar with its performance."

Komos adds that TA provides ULSD at approximately 135 to 140 sites nationwide, and those sites can be found on www.tatravelcenters.com.


Perceived lower lubricity with ULSD has many maintenance professionals wondering about fuel additives. As of January 2005, all highway diesel fuel sold in the U.S. must meet a new ASTM fuel lubricity standard (ASTM D 975). Any fuel lubricity additives necessary to meet this new specification will be added by the fuel suppliers. EPA says end-users do not need to add fuel lubricity additives.

Vic Meloche, manager, Technical Sales Support for Detroit Diesel in Detroit, MI, explains that ULSD has been formulated with the necessary additives to ensure that it does not harm fuel injection parts. Detroit Diesel does not endorse any specific aftermarket additive for use in any diesel fuel.

The company says that when switching from LSD to ULSD fuel, certain types of seals can shrink and develop small leaks in the form of seepage or drips.

EPA offers that in some instances, the introduction of ULSD fuel to older vehicles may affect fuel system components or loosen deposits in fuel tanks. Maintenance managers should closely monitor diesel-powered vehicles for potential fuel system leaks or premature fuel filter plugging during the changeover to ULSD fuel.


"The process to remove sulfur removes aromatic and density properties of the fuel," says Kelly. "The average loss in energy (BTU) content is around one percent, but is within the normal variability of diesel fuel. Every batch of diesel fuel is slightly different from the next."

Detroit Diesel concurs and explains that power and fuel economy may drop up to one to three percent with the use of ULSD on these engines.

Concerns about high underhood temperatures are false worries, according to Bob Stanton, director of Polk County Fleet Management in Bartow, FL. "Current testing is showing only slightly elevated temperatures in isolated areas," he says.

Stories of cold flow issues in northern climates have also created some concerns, but there is a "winter blend" of ULSD and kerosene.

"The sophisticated fleet knows how to have the right kind of fuel for the right environment," says Stuart. "Those not in the know may have problems without the kerosene-blended fuel for cold weather driving."


Switching from Low Sulfur Diesel to ULSD will warrant using a new, lower sulfated ash oil, CJ4.

"You have to change to a CJ4 oil—an added expense," says Stuart. "This new formulation offers one percent sulfated ash and is backwards compatible."

Stuart continues, "The problem with fleets is that we like one oil, which is currently CI4. However, you don't want to use the wrong oil—warranties could be violated."


"The biggest hurdle I see is the cleaning of the traps," says Stuart. "They're about the size of a trash compactor. If they go unattended, the exhaust will become plugged."

These "traps," or Diesel Particulate Filters (DPF), are used by engine OEMs and catch particulate matter, a.k.a. soot, to burn into ash.

"DPF cleaning intervals will vary by each vehicle's duty cycle," says Stanton. "Vocational trucks (dump trucks, refuse) will likely require cleaning more often than over-the-road units due to the sustained high load/high temperature operation common to OTR applications."

Stanton offers that service times for cleaning DPFs range from 1.5 to 3 hours and typical shop tools are not sufficient for cleaning. Companies including Donaldson Company and SPX Corporation have devised DPF Cleaning Systems. The machines will be standard service items at OEM dealerships offering both on-site DPF cleaning and DPF exchanges to their customers.

"One thing maintenance folks should remember about the new vehicles is that they absolutely cannot touch the exhaust system as they used to," says Stuart. "It's a sophisticated part of the emissions and you can't modify it or get creative with it. Use OEM parts only."

He adds, "The rest will be OJT as needed. We have a much higher level of sophistication with many systems, but, a piston is still a piston and a ring's a ring. Know the basic maintenance principles and all will be well."


API's Kelly offers that centrally-fueled fleets with tanks of 550 gallons of diesel share many of the same requirements as retail stations and are subject to EPA warnings and fines, which currently are $32,500 maximum per day, per occurrence.

"The biggest issue is to manage the integrity of the product during transition and make sure the proper signage is displayed throughout," says TA's Komos.

According to NSTA's Pudlewski, perhaps the single most important change will be the vehicles that require active regeneration of exhaust particulate matter in the vehicle's DPF. "If this event is not managed by the driver or mechanic," he explains, "the vehicle's electronic management system will adjust the operating parameters of the engine and cause the operator of the fleet to be out of compliance with Federal EPA requirements."


EPA says annual emission reductions will be equivalent to removing the pollution from more than 90 percent of today's trucks and buses when the current heavy-duty vehicle fleet has been completely replaced in 2030.

"Cleaner exhaust emissions are always a good thing," says Kelly. "The bigger positive is that ULSD improves public perception of diesel to think that this is not a dirty fuel. Auto manufacturers would like to offer more diesel-fueled vehicles because of diesel's fuel economy."

"I think we're a year away from serious conversation about failures related to Y2007 emission engines," says Stuart. "The level of repairs and failures will dictate changes in manufacturing, but I don't anticipate much."

He adds, "We get hung up on what's to come instead of what's under our nose. With the ULSD transition, the fears have not been realized. Early concerns generate a preparedness and we were prepared for the changeover."