Fleet Maintenance - 24

ly changing the fuel filters is required to prevent
contaminants from entering the fuel system," says
Navistar's Nachtman. "Purchasing fuel from a
high-volume filling station can help ensure fuel
is free from moisture or contaminants."
Verifying the quality of fuel, preventing algae
growth in tanks, and avoiding misuse of fuel additives also helps to ensure the optimized performance of diesel fuel, says Paccar's Sproull.
Lower viscosity oils
"Engines run hotter than they did 30 years ago, so
oils have had to change to withstand that higher
heat and to protect the engines," explains Shell
Lubricants' Arcy.
Federal emissions standards in 1998, 2004,
2007, and beyond dictated changes to the requirements of engine oil to be used in engines. This is
because the combustion process changed, with an
increased amount of PM, or soot, generated. The
PM was then captured by oil.
As engine manufacturers worked through
these design changes in order to meet federally
mandated emissions reductions - specifically with designs that delayed injection timing
and the introduction of exhaust gas recirculation (EGR) - more PM was generated during
the combustion process and deposited into the
crankcase, says Arcy.
"As we've changed and gone to things like selective catalytic reduction (SCR) to take care of NOx
emissions, they've been able to advance injection timing and run some lower EGR rates," Arcy
explains. "As a result of those things happening,
instead of taking care [of] NOx in the cylinder,
[the system takes] care of it in the exhaust pipe.
So, soot levels have been reduced dramatically."
Now that engine oil formulas have been
adjusted to withstand higher temperatures, and
less PM is trapped in engine oils, oil companies
are looking to additional changes to engine oil
composition to further improve system efficiencies. One of those is continual advancements
in creating lower viscosity engine oils. Lower
viscosity oils inherently improve efficiency
because less work is required to move the oil
through the system, which translates to less
internal resistance.
In December of 2016, to address changes in
the requirements of heavy duty engine oils, the
American Petroleum Institute (API) released its
latest round of oil grade specifications - FA-4
and CK-4 - as a follow-up to the CJ-4 engine oil
standards.
"Newer engines run at higher temperatures,
where conventional lubricants can be stressed,
and the rate of oxidization and degradation is
accelerated," says Ron LeBlanc Sr., senior technical advisor for lubricant and grease developer Petro-Canada Lubricants. "The latest engine
oils are more resistant to oxidation, they have
increased shear stability, and have lower viscosity - specifically the FA-4 category - which leads
to lower engine oil flow resistance in the engine
and a reduction in fuel consumption, while still
offering increased levels of wear protection."
Engine oils meeting the CK-4 engine oil specification are backward compatible with CJ-4 engine
oils. FA-4 engine oils have lower viscosity grades to
meet the needs of next-generation diesel engines.

24 Fleet Maintenance | October 2019

» Lower viscosity oils inherently improve efficiency because less work is required to
move the oil through the system, which translates to less internal resistance.
Photo courtesy of Shell Lubricants

A review of emissions byproduct
and fuel efficiency terms
What's the
difference between
CO2 and NOx?
Are soot and ash
the same? Get
answers here.
While governmental regulations, overseen by the U.S.
Environmental Protection
Agency (EPA), continue to
focus on reducing vehicle
emissions, there are a number
of terms that require definition in order to understand
the full scope of how the
requirements impact vehicle
performance and efficiency, as
it relates to the powertrain.
The heavy duty diesel engine
aftertreatment system is
designed to limit the amount
of exposure for particulate
matter (which includes carbon
monoxide, or CO2) and nitrogen
oxide (NOx) emissions. There
are two primary systems to
help capture these emissions
before they're emitted into the
atmosphere: the exhaust aftertreatment technology - which
includes the diesel oxidation
catalyst (DOC) and diesel particulate filter (DPF) - to capture
particulate matter; as well as a

select catalytic reduction (SCR)
system, and an exhaust gas
recirculation (EGR) system, to
help reduce NOx emissions.
"High black smoke [particulate
matter] can put a bigger burden
on the diesel particulate filter.
Similarly, high NOx can put
a bigger burden on the SCR
system," says Kris Ptasznik, X15
product manager, Cummins.
"Engines equipped with an
EGR to control NOx require
higher injection pressures
for better mixing," Ptasznik
adds. "Reduced NOx enables
[the] engine and [the aftertreatment] system to reduce
fuel and urea consumption."
Here's a review of the
most common components and terms:
Diesel particulate filter
(DPF) system - This system
is designed to capture the particulate matter (PM) generated
from the combustion process.
Diesel oxidation catalyst
(DOC) - This part of the
aftertreatment system oxidizes carbon monoxide and
hydrocarbons in order to limit
emissions.

Carbon monoxide (CO) - The
residual material left during
the combustion process of
diesel fuel or gasoline. It is a
byproduct of incomplete combustion of the fuel and can be
damaging to the environment.
Particulate matter (PM)
- Particulate matter, which
includes dirt, dust, and soot,
is the byproduct material created by the engine after the
fuel combustion process. With
present-day aftertreatment
systems, the DPF is designed
to capture PM. The DPF should
be periodically cleaned on the
vehicle, through a regeneration process, and replaced at
regular intervals, to ensure
continued collection of PM.
Ash - Ash is the leftover
residue remaining in the DPF
after PM, or soot, is captured.
This is the material that accumulates in the DPF media.
Nitrogen oxide (NOx) - The
SCR system is designed to
capture NOx before it leaves
the vehicle system and enters
the atmosphere. The SCR
system uses diesel exhaust
fluid (DEF), also known as urea,
to create a chemical reaction
that breaks down the NOx.

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