Fleet Maintenance - 30

SPOTLIGHT ON FLUIDS & FILTRATIONS

The lowdown
on grease

		┬╗Grease's primary goal as a lubricant is to separate the mating surfaces of
components by creating a lubricant film between contact stress points.
177079291 | Vitpho | Dreamstime.com

Basic knowledge and
best practices for
keeping fleet vehicles
properly lubricated.
By Tyler Fussner

L

ubrication is an essential aspect of commercial
vehicle maintenance. In order to provide adequate
and necessary lubrication, a fleet needs to understand the nuances of one of the most important
lubricating agents: grease. There is a wide range of
greases available today suitable to an even wider
range of applications. Understanding what grease
to use for each application can help a fleet's maintenance efforts in assuring vehicles and operations run smoothly.

The composition of grease

Grease can be understood as a mixture of oil,
additives, and a thickening agent, referred to as
a thickener.
"A lubricating grease is typically composed of 50
to 90 percent base oil, 3 to 5 percent thickener, and
2 to 10 percent additives," says Ron LeBlanc Sr.,

30 Fleet Maintenance | August 2020

senior technical services advisor, Petro-Canada
Lubricants. Petro-Canada Lubricants is a developer and producer of lubricants, specialty fluids,
and greases.
There exists a wide range of additives used in
grease which serve as protective agents.
"[Within a grease formulation,] we have antiwear additives or extreme pressure additives,
antioxidant-type additives to protect the grease
under high-temperature conditions, and antivirus or anti-corrosion additives in the grease as
well," says Stede Granger, OEM technical services
manager at Shell, a global group of energy and
petrochemical companies.
Thickener serves an important role in a grease.
Kuldeep Mistry, product development specialist at
Timken, a designer of bearings and power transmission products, compares the role of a thickener
to that of a sponge. The concept of a sponge holding water and releasing that water under pressure can apply to thickener in grease, wherein the
thickener holds the oil within the grease. When
the grease is placed under heat and pressure, the
molecules are broken down into smaller pieces, a
process known as shear. This process releases the
oil to the component for lubrication.
"When the grease is subjected to mechanical
work, it releases the base oil and additives to
lubricate the components, whether it's rolling

elements of wheel bearings, sliding surfaces of
a fifth wheel, et cetera," LeBlanc says. "When
the rolling elements stop and the grease cools, it
returns to its original texture. This is called thixotropic behavior."
Certain thickeners can provide improved shear
performance within the grease.
"For the fleet application, you need lithium or
lithium complex thickener because they have
excellent shear stability," Mistry continues. "They
have very good high temperature performance.
This makes a lithium-base grease a great candidate to attain the long lubrication grease life to
support the bearing."
There are many options when it comes to thickening agents within a grease.
"Some thickeners in greases available in today's
market include aluminum complex, lithium, lithium complex, calcium, and calcium sulfonate
complex," LeBlanc says. "Greases can also contain
solid lubricants such as molybdenum disulfide,
graphite, and others."
The majority of a grease's composition consists
of its base oil. There are differences between greases utilizing conventional oils or synthetic oils that
fleets should be aware of.
According to Granger, the additives for greases
with conventional or synthetic base oils would
be similar, as well as their viscosity. Often, he
suggests, greases that have a mineral base oil
cost less.
"The advantages of the synthetic oil over the
mineral oil is that the synthetic oils have better
cold temperature properties," Granger continues.
"The grease will pump better, operate better, cause
less drag, and perform better in cold temperatures."
It is not only the cold temperature performance
that synthetic oils excel in, but high-temperature
environments as well.
"The other place that synthetic base oils do
better in is [their] ability to handle higher temperatures for longer periods of time," Granger says. "If
the grease is going to be in a hot environment, then
the synthetic is a better choice."
The difference in performance between conventional and synthetic oil can be understood
through their respective molecular compositions
resulting from their refining processes.
"When we take crude oil out of the ground, it
is a mixture of all kinds of different components,
and part of the refining process is to separate those
components," Granger explains. "We separate out
the lighter molecules from the heavier molecules
to make a lighter base oil. We're separating the
hydrocarbons, but it's an approximation, so we
get a [varying] mixture of components. When we
create a synthetic base oil, that is typically very
pure, and it has the right molecules. As a result, we
have components in the mineral oil that don't do
very well at the higher temperatures, whereas the
synthetic oil is [comprised of] the molecules that
we want that do handle the high temperatures."
Furthermore, synthetic base oil greases generally have a higher viscosity index (VI). The VI
reveals how the oil changes with temperature.
The higher the VI, the less the oil changes with
temperature. Granger says that Shell includes VI
improving additives to conventional mineral oil
to avoid drastic changes in varying temperatures.


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Fleet Maintenance

Table of Contents for the Digital Edition of Fleet Maintenance

Uptime: Wireless Data and the Future of Right to Repair
Editor's Note: Information Overload
Vehicles: Considerations for Winterizing Vehicles
In The Bay: Repair Information Resources to Help Drive Technician Productivity
Shop Operations: Extensive Service Networks to Improve Vehicle Uptime
Keeping Up with EGR Systems
The Lowdown on Grease
Management: Guard Against Mental Fallacies
Diagnostics: Scope Diagnostics Brings Heavy Duty Electrical Issues Into Focus
Training: ASE Entry-Level Certification
Fleet Parts & Components
Tools & Equipment
Classifieds
Guest Editorial: Considerations When Upgrading Vehicles to Steerable Lift Axles
Fleet Maintenance - 1
Fleet Maintenance - 2
Fleet Maintenance - 3
Fleet Maintenance - 4
Fleet Maintenance - 5
Fleet Maintenance - 6
Fleet Maintenance - 7
Fleet Maintenance - Uptime: Wireless Data and the Future of Right to Repair
Fleet Maintenance - 9
Fleet Maintenance - Editor's Note: Information Overload
Fleet Maintenance - 11
Fleet Maintenance - Vehicles: Considerations for Winterizing Vehicles
Fleet Maintenance - 13
Fleet Maintenance - 14
Fleet Maintenance - 15
Fleet Maintenance - 16
Fleet Maintenance - 17
Fleet Maintenance - In The Bay: Repair Information Resources to Help Drive Technician Productivity
Fleet Maintenance - 19
Fleet Maintenance - 20
Fleet Maintenance - 21
Fleet Maintenance - 22
Fleet Maintenance - 23
Fleet Maintenance - Shop Operations: Extensive Service Networks to Improve Vehicle Uptime
Fleet Maintenance - 25
Fleet Maintenance - 26
Fleet Maintenance - 27
Fleet Maintenance - Keeping Up with EGR Systems
Fleet Maintenance - 29
Fleet Maintenance - The Lowdown on Grease
Fleet Maintenance - 31
Fleet Maintenance - Management: Guard Against Mental Fallacies
Fleet Maintenance - 33
Fleet Maintenance - Diagnostics: Scope Diagnostics Brings Heavy Duty Electrical Issues Into Focus
Fleet Maintenance - 35
Fleet Maintenance - Training: ASE Entry-Level Certification
Fleet Maintenance - 37
Fleet Maintenance - Fleet Parts & Components
Fleet Maintenance - 39
Fleet Maintenance - 40
Fleet Maintenance - Tools & Equipment
Fleet Maintenance - 42
Fleet Maintenance - 43
Fleet Maintenance - 44
Fleet Maintenance - Classifieds
Fleet Maintenance - Guest Editorial: Considerations When Upgrading Vehicles to Steerable Lift Axles
Fleet Maintenance - 47
Fleet Maintenance - 48
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