Edelweiss
Guru
Some interesting facts about the qualities and problems of Ultra Low Sulfur Diesel.
*
<h5>Lubricity</h5>
The most immediate concern with ULSD certainly the one that has received the most publicity is lubricity. When diesel fuel is refined to make ULSD, it is reacted with hydrogen to remove the sulfur. This process also removes much of the fuels lubricity. (Many people mistakenly believe that it is only the sulfur that supplies lubricity.) Lubricity is essential in diesel fuel to reduce friction at finely machined pumps and injectors; without sufficient lubricity, a diesel would grind itself to a premature death.
Minimum lubricity is a requirement of the ASTM-D975 standard, which means oil companies must use either soy biodiesel or a synthetic additive to return fuel to its pre-ULSD lubricity levels. Soy biodiesel has the potential to loosen built-up gunk in the tank and clog filters, but not to the extent that ethanol did with gasoline tanks. Note, however, that a synthetic additive is more likely to be used, since it is less expensive and more stable than soy.
*Cetane
Diesels rely on compression (and not a spark) to ignite the fuel. A higher cetane number means the fuel will ignite more readily, run smoother and produce less smoke. All diesel fuel must have a cetane rating of at least 40. Most regular diesel fuel has a cetane rating of 43 to 45, which should be fine for most boat engines. The good news is that the cetane numbers remained the same with ULSD.
Using an additive to boost cetane may help your engine, but be aware that an independent study of 19 additives sold to improve an engines cetane rating found that five had no significant effect on the fuels cetane rating and four additives significantly lowered the cetane content.
*Corrosion
Since ULSD was introduced in 2006, some suppliers have reported accelerated corrosion in underground steel storage tanks. The cause is unclear and no one is certain whether it is related to ULSD, an additive, or something that occurred during the transition from low sulfur diesel (LSD) to ULSD. (Curiously, in Europe, where ULSD has been in use for much longer, there have not been any corrosion issues, according to a report in Fuel Oil News.) The only solution, thus far, is to keep tanks as clean as possible with no water bottoms so there is nothing for the fuel to react with. On boats, repairers we talked with had not seen any indications of corrosion problems.
*Leaking Gaskets
When the transition was made to LSD in 1993, there were problems with leaking gaskets. Newer gaskets that resist leaking were developed, but there were some fears that the gaskets might not stand up to ULSD. After talking to numerous marina owners and engine manufacturers, leaking gaskets dont appear to be a problem.
*
<h5>Water and Bugs</h5>
Microbial growth bugs needs water to grow and has always been a concern with diesel fuel. ULSD holds less water than older, higher-sulfur fuels. While that sounds like good news, its not; any water that finds its way into a boats tank is less likely to be absorbed into the fuel and is more likely to wind up at the bottom of the tank, where it can help spawn the dreaded microbial bugs. Biocides kill bugs (as will freezing temperatures), but their tiny little carcasses accumulate at the bottom of the tank and form a funereal goo. Its possible that tanks may need to be cleaned more often to prevent filter clogging and corrosion.
The best defense is to keep water out of your fuel by keeping the tank topped off to reduce condensation, only buying fuel from a reliable source, and checking your water separator. If water starts to appear routinely, youll have to take steps to clean your tank and polish the fuel.
Cold Weather
The refining process used to lower the sulfur content of ULSD also can affect the content of naturally occurring paraffin (wax) in diesel fuel, which causes it to gel more readily in cold weather. For the vast majority of boat owners, who lay up their boats over the winter, cold weather starting isnt a concern. For anyone who plans to use their diesel in winter, distributors compensate for colder temperatures by selling a winter blend. If you still have a summer blend in the tank, youll need to use a coldweather additive and follow the instructions. Use only the recommended dose, as too much additive may make gel problems worse.
*fuel Source
A reliable source for your fuel is (and has always been) very important. A high-volume dealer is far more likely to have fresh fuel than a sleepy, backwater marina. As a general rule, diesel fuel can be expected to remain healthy for at least a year. The major oil companies or distributors will sometimes use their own additives (antioxidants and biocides). If the fuel has been treated and stored in a clean (no rust), water-free tank that is in a cool (or underground) climate, diesel fuel can last as long as three years
An excerpt from Seaworthy Magazine
-- Edited by Edelweiss on Saturday 8th of October 2011 01:09:07 AM
*
<h5>Lubricity</h5>
The most immediate concern with ULSD certainly the one that has received the most publicity is lubricity. When diesel fuel is refined to make ULSD, it is reacted with hydrogen to remove the sulfur. This process also removes much of the fuels lubricity. (Many people mistakenly believe that it is only the sulfur that supplies lubricity.) Lubricity is essential in diesel fuel to reduce friction at finely machined pumps and injectors; without sufficient lubricity, a diesel would grind itself to a premature death.
Minimum lubricity is a requirement of the ASTM-D975 standard, which means oil companies must use either soy biodiesel or a synthetic additive to return fuel to its pre-ULSD lubricity levels. Soy biodiesel has the potential to loosen built-up gunk in the tank and clog filters, but not to the extent that ethanol did with gasoline tanks. Note, however, that a synthetic additive is more likely to be used, since it is less expensive and more stable than soy.
*Cetane
Diesels rely on compression (and not a spark) to ignite the fuel. A higher cetane number means the fuel will ignite more readily, run smoother and produce less smoke. All diesel fuel must have a cetane rating of at least 40. Most regular diesel fuel has a cetane rating of 43 to 45, which should be fine for most boat engines. The good news is that the cetane numbers remained the same with ULSD.
Using an additive to boost cetane may help your engine, but be aware that an independent study of 19 additives sold to improve an engines cetane rating found that five had no significant effect on the fuels cetane rating and four additives significantly lowered the cetane content.
*Corrosion
Since ULSD was introduced in 2006, some suppliers have reported accelerated corrosion in underground steel storage tanks. The cause is unclear and no one is certain whether it is related to ULSD, an additive, or something that occurred during the transition from low sulfur diesel (LSD) to ULSD. (Curiously, in Europe, where ULSD has been in use for much longer, there have not been any corrosion issues, according to a report in Fuel Oil News.) The only solution, thus far, is to keep tanks as clean as possible with no water bottoms so there is nothing for the fuel to react with. On boats, repairers we talked with had not seen any indications of corrosion problems.
*Leaking Gaskets
When the transition was made to LSD in 1993, there were problems with leaking gaskets. Newer gaskets that resist leaking were developed, but there were some fears that the gaskets might not stand up to ULSD. After talking to numerous marina owners and engine manufacturers, leaking gaskets dont appear to be a problem.
*
<h5>Water and Bugs</h5>
Microbial growth bugs needs water to grow and has always been a concern with diesel fuel. ULSD holds less water than older, higher-sulfur fuels. While that sounds like good news, its not; any water that finds its way into a boats tank is less likely to be absorbed into the fuel and is more likely to wind up at the bottom of the tank, where it can help spawn the dreaded microbial bugs. Biocides kill bugs (as will freezing temperatures), but their tiny little carcasses accumulate at the bottom of the tank and form a funereal goo. Its possible that tanks may need to be cleaned more often to prevent filter clogging and corrosion.
The best defense is to keep water out of your fuel by keeping the tank topped off to reduce condensation, only buying fuel from a reliable source, and checking your water separator. If water starts to appear routinely, youll have to take steps to clean your tank and polish the fuel.
Cold Weather
The refining process used to lower the sulfur content of ULSD also can affect the content of naturally occurring paraffin (wax) in diesel fuel, which causes it to gel more readily in cold weather. For the vast majority of boat owners, who lay up their boats over the winter, cold weather starting isnt a concern. For anyone who plans to use their diesel in winter, distributors compensate for colder temperatures by selling a winter blend. If you still have a summer blend in the tank, youll need to use a coldweather additive and follow the instructions. Use only the recommended dose, as too much additive may make gel problems worse.
*fuel Source
A reliable source for your fuel is (and has always been) very important. A high-volume dealer is far more likely to have fresh fuel than a sleepy, backwater marina. As a general rule, diesel fuel can be expected to remain healthy for at least a year. The major oil companies or distributors will sometimes use their own additives (antioxidants and biocides). If the fuel has been treated and stored in a clean (no rust), water-free tank that is in a cool (or underground) climate, diesel fuel can last as long as three years
An excerpt from Seaworthy Magazine
-- Edited by Edelweiss on Saturday 8th of October 2011 01:09:07 AM