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Added Value — Does your diesel need a fuel additive?

Posted: January 10, 2019 by Jim Park

Canadian diesel is chemically consistent, but do you still need a fuel additive?

TORONTO, Ont. — Canadian fleets have few advantages over their American counterparts, but overall we have a better quality of diesel fuel than they do, and it’s chemically more consistent across the country. In the U.S., fuel quality can vary considerably from region to region and from supplier to supplier — even from truckstop to truckstop.

Americans are big consumers of fuel additives to help make up for those inconsistencies. The most Canadian fleets have to worry about, besides price, is cold-weather performance.

Still, many Canadian fleets — especially those with lots of U.S. exposure — would probably confess to treating their fuel with additives of some description. Some use detergent additives or lubricity agents to make up for the loss of sulfur in diesel fuel. Others use fuel stabilizers to offset the effects of aging and cetane improvers to optimize combustion, or in the words of some additive suppliers, “to increase horsepower and reduce emissions.”

It’s easy to be skeptical of such claims, and in most cases you’ll never know if the product is working or not. Take the claim of some additive makers that their products reduce harmful deposits on injectors. How does one gauge the condition of an injector short of tearing it down and examining it? If it fails, you might do that, but if it doesn’t fail over its expected life, is that a result of the additives you used?

In other instances, it’s easier to tell if a product is working. If you suffer from plugging fuel filters, for example, an additive can help dissolve the asphaltenes in the fuel. These hydrocarbons with a high molecular weight are usually found on the bottoms of the crude. They can also form in ultra-low-sulfur diesel  (ULSD) because of the heat created by higher pump pressures inside the fuel system and returned to the tank from your fuel pressure regulator, notes Kevin Adams, director of research and development, Lubrication Specialties Inc.

“High-performance fuel additives can contain ingredients that not only dissolve the asphaltenes that are already present in your fuel, but also to help prevent asphaltenes from forming and plugging filters,” he says. “Additionally, many trucks suffer from the effects of a low cetane rating within the fuel that causes poor fuel economy and hard starts during the cold months. A good fuel additive will boost the cetane number and solve each of these fuel-related issues.”

Diesel fuel quality

Diesel engine makers need to account for swings in quality when designing and certifying their engines. Generally, they do not endorse or recommend the use of fuel additives.

“We do not recommend that Volvo truck owners add additives to diesel fuel. If additives are needed, it should be done at the fuel supplier terminal,” says John Moore, powertrain product marketing manager at Volvo Trucks North America.

Cummins, on the other hand, surprised us last year by officially endorsing a fuel additive, recommending two Power Service products — Diesel Kleen + Cetane Boost and Diesel Fuel Supplement + Cetane Boost.

“Cummins engines are designed, developed, rated and built to both certify and operate efficiently on commercially available diesel fuel,” said Josh Hahn, coolants and chemicals business leader at Cummins Filtration. “However, Cummins recognizes that there are poor quality fuels on the market which don’t always meet ASTM D975 [the U.S. diesel fuel standard], and these fuel issues can result in a variety of issues for the customer, such as poor lubricity, low cetane numbers, low temperature operability issues, or injector deposits. Some cold weather operations may also call for the use of fuel additives when pour-point depressants, wax-crystal modifiers or de-icers are needed.”

When Cummins announced the Power Service partnership last year, director of technical quality and materials engineering for Cummins Roger England said: “In recent years, diesel fuel quality has become increasingly important as engines evolve and the diesel fuel manufacturing processes change.”

Meanwhile, Detroit Diesel says it does not have any specific requirements beyond current ASTM spec’s, but it does suggest customers take steps to ensure they are using a quality fuel.

“Detroit does not specifically endorse any brand or type of fuel additive, but we recommend Top Tier diesel fuel as it addresses many of the shortcomings of ASTM specifications regarding diesel fuel quality,” says Jason Martin, manager, HDEP thermodynamics and fuel map management at Daimler Trucks North America. “Top Tier is a voluntary retailer program that addresses the stability and lubricity of fuel, detergency, water and particulates — items that help maintain the performance of the fuel system over the lifetime of the engine, which is a contributing factor to ensure top engine performance.”

Top Tier diesel is available through many retailers in North America. The website notes, “Since retailers may also sell non-additized diesel fuel or diesel not meeting the Top Tier requirements, always check the dispenser for Top Tier Diesel Fuel.”

Minimum cetane numbers

Many additive products claim to improve cetane numbers. A fuel supply’s natural cetane number is influenced by several factors such as the base crude stock and the refining process. The minimum cetane number in the United States is 40, but actual numbers will vary. In Europe the minimum is number 51.

Higher is viewed as better, up to a point.

A BP oil website from the U.K. offers a clear and concise description of cetane and its effect on performance: “The cetane number is the key measure of diesel fuel combustion quality. The number relates to the ignition delay — the period that occurs between the start of fuel injection and the start of combustion. Good quality combustion occurs with rapid ignition followed by smooth and complete fuel burn: the higher the cetane number, the shorter the ignition delay and the better the quality of combustion. Conversely, low cetane number fuels are slow to ignite and then burn rapidly. These poor combustion characteristics can give rise to excessive engine noise and vibration, increased [soot] emissions [from incompletely burned fuel] and reduced vehicle performance.”

How do you know if you need a cetane improver? If you buy low-quality diesel then the improver will help, but if you already have a good fuel supplier then the additive isn’t going to hurt you, but it might not be required.

“Filling at different locations you’ll see a variation in the fuel quality,” says Pierre Barras, key account manager for process oils and special fluids at Total Canada. “I would say there is a benefit to adding something on a regular basis just to make sure that you cover all your bases. You might not need it, but you won’t know. When you do need it you still might not know, and your fuel economy can suffer.”

There are many reasons to consider investing in an additive program, from increasing fuel mileage to reducing diesel particulate filter soot loads, maintaining good injector performance, and reducing corrosion within the fuel system. Products are available that can accomplish all that and more. But there is a lot of product on the market that’s little more than colored kerosene.

It can be difficult to see the benefits of a good additive program for several reasons, says Barras “A lot of people have tried products that didn’t work, or they didn’t do a thorough evaluation of the product and they didn’t see the performance improvements,” he says. “The other problem is they lose sight of the benefits over time. If a product claims it will help your engine last 10% longer, you won’t see that for eight or 10 years.

“The other problem can be the with the scope of the improvement,” Barras says. “If you get a 3% improvement in fuel mileage, it can be lost in imprecise testing and evaluation. Your variation might be as high as 5%. The gains get lost in the noise.”

Are you confident that your fuel won’t gel?

Do you need additives
when using ‘winter diesel’?

In the midst of a Canadian winter, it’s normal to worry about gelled diesel fuel. But how much of a concern is it really? Did that last jug of anti-gel additive keep you going through the cold dark night, or was the fuel already blended for cold-weather operation. Many Canadian fuel suppliers offer a winter fuel that’s blended specifically for cold weather, and that may be enough in most cases to prevent gelling.

“Diesel fuel is blended to meet the requirement for the region and time of use, so a blend delivered to Toronto at this time of year is considerably different than one blended for Edmonton or Vancouver,” says Suncor spokeswoman Nicole Fisher. (Suncor owns Petro-Canada). “That being said, winter blends use more ‘light’ diesel components that have better cold weather operability. Refineries also have a ‘winter mode,’ where they run some of the units differently or run some units only in the winter to produce diesel components that can be blended together to meet the cold weather operability.”

Fisher says Suncor (and others) produce fuel to meet Canadian conditions by looking at 30 years of weather and temperature data for various regions or zones around the country and then produce diesel to meet the requirement for any given zone. “For instance, Ontario has eight different temperatures zones, while Alberta has three and Yukon has only one,” she says. “In almost all provinces, the answer is a large range from the minus 20s to the minus 40s, excluding the Vancouver area where -10 C is as low as we need to go.”

If the fuel you’re buying doesn’t stray too far from home, chances are you’re protected. But if you buy it in a mild zone, like Vancouver or Toronto and then head north, you may want to add a jug of prevention to the fuel before you leave.

“You have to add the product before the temperature drops,” cautions Pierre Barras, key account manager for process oils and special fluids at Total Canada. “The product can retard the formation of crystals, but it will not destroy crystals once they have formed. You have to add it before the temperature reaches a critical point.”

 

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