16
MARINE TECHNICIANTODAY | SUMMER 2015
TECH TALK
In 1991, the NLGI developed a classification system specifically
targeting automotive greases (Table One). For the majority of readers,
it is the appropriate rating system for your applications.
So when you are looking to purchase grease for your truck, look for grease
labeled GC-LB: grease rated for severe duty for the wheel bearings as
well as for the chassis. Multi-purpose grease is the correct match for
chassis and wheel bearings but heavy duty grease is the better choice
for extreme loads exceeding 10,000 pounds. Synthetic greases will
provide the best protection over the widest temperature range. Heavy
duty grease is moly-fortified (molybdenum disulfide) which provides for
extreme pressure lubrication. I have explained the difference in extreme
pressure lubrication vs standard lubrication regimes in an earlier issue,
so please refer to that issue for the specific explanation. There are
several legitimate extreme pressure grease points on heavy duty trucks;
using the correct grease is critical for proper operation and long life.
If the grease will be exposed to water, either by submersion or by spray,
using water resistant grease is the best choice. To be water resistant,
the grease must pass additional testing that insures its ability to cling
to a surface while being sprayed with a stream of water. Water resistant
greases contain additional thickeners and tackifiers that allow them to
resist washing out. Sometimes, these greases will be labeled “marine,”
but more and more they are simple referred to as water resistant.
GREASE COMPATIBILITY
A word of caution; not all greases are compatible with each other. This
problem occurs because some of the thickening agents chemically
react with others, which can lead to the grease becoming very hard or
liquefying or preventing the oil from leeching out to provide lubrication,
essentially rendering the grease useless. Grease comes mixed in
a variety of thickeners (soaps) such as, lithium or lithium-complex,
calcium compounds, barium, aluminum to name a few: they are not
always compatible with each other. Table Two covers compatibility/
incompatibility of commonly-used greases. If you find grease that uses
a different thickener than those listed, contact me to verify compatibility.
Grease is the forgotten lubricant. It just doesn’t rise to the level of notice
of other lubricants; however, grease is fundamental to proper care for
your boat trailer, out-drive and vehicle. For most applications, greasing
should be done at three month intervals for petroleum and six month
intervals for synthetics. Wheel bearings properly packed with synthetic
grease are good for 10 years, but trailer bearings need to be full to
prevent water intrusion. Bearing buddies are a good addition to trailer
hubs. There are few automobile manufacturers stipulating wheel bearing
maintenance, and some are now installing sealed bearings that cannot
be greased. Ball joints and steering joints can still be greased in most
heavy duty vehicles, but in light duty vehicles, the grease fittings may not
be installed and you will have to purchase them and install them. As with
all lubricants, synthetic greases outperform petroleum greases, and the
cost difference is actually in favor of the synthetics; you simply use less
grease over time and the upfront cost difference is minimal.
For questions or comments contact Dan Watson, Certified Lubrication Specialists STLE,
at the following
800-370-2986 or
Aluminum Complex
Barium Complex
Calcium Stearate
Calcium 12 Hydroxy
Calcium Complex
Calcium Sulfonate
Clay Non-soap
Lithium Stearate
Lithium 12 Hydroxy
Lithium Complex
Polyurea Conventional
Polyurea Shear Stable
Aluminum Complex
I
I
C I
B I
I
I
C I
C
Barium Complex I
I
C I
C I
I
I
I
I
B
Calcium Stearate I
I
C I
C C C B C I
C
Calcium 12 Hydroxy C C C
B B C C C C I
C
Calcium Complex I
I
I
B
I
I
I
I
C C C
Calcium Sulfonate B C C B I
I
B B C I
C
Clay Non-soap I
I
C C I
I
I
I
I
I
B
Lithium Stearate I
I
C C I
B I
C C I
C
Lithium 12 Hydroxy I
I
B C I
B I
C
C I
C
Lithium Complex C I
C C C C I
C C
I
C
Polyurea Conventional
I
I
I
I
C I
I
I
I
I
C
Polyurea Shear Stable C B C C C C B C C C C
Table Two – Compatibility / Incompatibility of Commonly Used greases
Table Two – Different types of grease are not always compatible with each other. For instance, the first
two grease compounds, Aluminum Complex and Barium Complex are incompatible as indicated by
the “I” inside a red box. A “C” inside a green box indicates that the two compounds are compatible with
each other. A “B” in a yellow field indicates the two compounds possess only borderline compatibility.
C
= Compatible
I
= Incompatible
B
= Borderline
