Locate the cloud point of the lighter fuel on the right side
of the table. Mark the point on the table.
Draw a line between the two points that were
established. Label this line "A".
Determine the lowest outside temperature for machine
operation. Find this point on the left side of the table.
Mark this point. Draw a horizontal line from this point.
Stop the line at the intersection of line "A". Label this
new line "C".
Draw a vertical line from the intersection of lines "A" and
"C". Stop the line at the bottom of the table. Label this
line "B". The point at the bottom of line "B" reveals the
percentage of lighter fuel that is required to modify the
The above example shows that the blending will require a thirty
percent mixture of lighter fuel.
Additives are a good method to use in order to lower the pour
point of a fuel. These additives are known by the following
names: pour depressants, cold flow improvers, and wax
modifiers. When the additives are used in a low concentration,
the fuel will flow through pumps, lines, and hoses. These
additives must be thoroughly mixed into the fuel at
temperatures that are above the cloud point. The fuel supplier
should be contacted in order to blend the fuel with the
additives. The blended fuel can be delivered to your fuel
Problems with fuel filters can occur at any time. The cause of
the problem can be water in the fuel or moisture in the fuel. At
low temperatures, moisture causes special problems. There
are three types of moisture in fuel: dissolved moisture
(moisture in solution), free and dispersed moisture in the fuel,
and free and settled at the bottom of the tank.
Most diesel fuels have some dissolved moisture. Just as the
moisture in air, the fuel can only contain a specific maximum
amount of moisture at any one temperature. The amount
becomes less as the temperature is lowered. For example, a
fuel could contain 100 ppm (0.010 percent) of water in solution
at 18°C (65°F). This same fuel can possibly hold only 30 ppm
(0.003 percent) at 4°C (40°F).
After the fuel has absorbed the maximum possible amount of
water, the additional water will be free and dispersed. Free
and dispersed moisture is fine droplets of water that is
suspended in the fuel. Since the water is heavier than the fuel,
the water will slowly become free and settled at the bottom of
the tank. In the above example, when the fuel temperature
was lowered from 18°C (65°F) to 4°C (40°F), 70 ppm of water
became free and dispersed in the fuel.
The small drops of water cause a cloudy appearance in the
fuel. If the change in temperature is slow, the small drops of
water can settle to the bottom of the tank. When the fuel
temperature is lowered rapidly to freezing temperature, the
moisture that comes out-of-solution changes to very fine
particles of ice instead of small drops of water.
The particles of ice are lighter than the fuel, and the particles of
ice will not settle to the bottom of the tank. When this type of
moisture is mixed in the fuel, this moisture will fill the fuel
filters. The ice crystals will plug the fuel filters in the same way
as wax plugs the fuel filters.
If a filter is plugged and fuel flow is stopped, perform the
following procedure to determine the cause:
Remove the fuel filters.
Cut the fuel filters open.
Inspect the fuel filter before the filter warms. This
inspection will show that the filter is filled with particles
of either ice or wax.
The moisture which is free and settled at the bottom of the tank
can become mixed with the fuel. The force of any pumping
action will mix the moisture with the fuel whenever fuel is
transferred. This moisture then becomes free and dispersed
water. This moisture can cause ice in the filters. This moisture
can cause other problems with filters at any temperature.
Generally, the same force that mixes the water into the fuel will
also mix dirt and rust from the bottom of the tank with the
water. The result is a dirty mixture of fuel and water which can
also fill the filters and stop fuel flow.