Fleet Maintenance - 15

Fuel system

Diesel fuel naturally contains paraffin wax. As
temperatures drop, the paraffin wax binds together and forms crystals. These crystals separate
from the diesel fuel and can potentially increase
in size as temperatures continue to fall, blocking
the vehicle's fuel filter. The process is called gelling
and is something fleets want to avoid at all costs.
To
prevent
gelling ,
David Lunsford, commercial marketing manager at
ExxonMobil, an oil and gas
provider, says to purchase
diesel fuel that is pre-blended with cold flow improvers.
"Cold flow improvers are
used to modify the shape
of the wax crystals so that
[diesel] fuel keeps flowing
through fuel filters at lower
temperatures," Lunsford says.
"Since the weather is not
always predictable, a cold
flow improver provides an
added margin of safety for
cold weather operability."
Kerosene blending is another option for cold weather
treatment, Lunsford adds.
"Kerosene is typically more
expensive and would need to
be blended at significant levels
to achieve the same results
as the cold flow improver,"
he says. "For best results, the
cold flow improver needs to
be fully dispersed in the fuel
at the appropriate treat rate."
Lunsford advises against
using aftermarket cold flow
additives, however.
"Adding additives to diesel
fuel can cause more harm than
good," he says. "Aftermarket
cold flow additives can interact poorly with cold flow additives blended into the fuel at the
refinery or the terminal, which
can result in filter plugging and
potentially worsen the fuel's
cold flow properties. In addition, in cold temperatures, aftermarket additives become less
soluble and may not dissolve
correctly in the fuel. Instead we
recommend purchasing diesel
fuel that is already additized for
winter conditions."

Lubricants' Granger. "When [the temperature] gets
cold, [oils] actually thicken up at a faster rate than
[they] thin at higher temperatures."
As oil thickens, it adds resistance to the engine,
making it more difficult to start the vehicle.
"Startup and pumpability is key," says Jason
Miller, heavy duty sales and strategy manager at
CITGO Lubricants, a manufacturer of oils, fluids,

and greases. "With engine oils, if the viscosity
is too high at low ambient temperatures, the oil
will not pump, meaning critical engine parts won't
receive the startup lubrication needed. Startup
is where the majority of engine wear happens."
Both CITGO Lubricants and Shell Lubricants
agree that fleets may want to consider transitioning to lower viscosity oils for the winter time.

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Oils and lubricants

The viscosity of oil - whether
engine oil, transmission oil,
axle oil, or any other kind -
changes with temperatures.
The lower the temperature,
the higher the viscosity.
"It's an exponential curve,
not a linear curve," says Shell

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August 2020 | VehicleServicePros.com

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Fleet Maintenance

Table of Contents for the Digital Edition of Fleet Maintenance