TM 5-685/NAVFAC MO-912
C-1. Diesel engine oil.
d. Changing oil. Lubricating oil must be changed
periodically. Refer to recommendations by the en-
Lubricating oil for diesel engines should comply
gine manufacturer to specific conditions, time inter-
with Federal Specifications MIL-L-2 104 and
vals, and instructions. General oil change proce-
MIL-L-9000. Oil that complies with the specifica-
dures are as follows:
tions produces acceptable amounts of carbon resi-
(1) Operate the engine before draining old oil.
due during engine use and has acceptable pour,
Oil should be drained while warm and immediately
flash, and fire points. Straight mineral oil is the
after engine shut down because contaminants are in
basic ingredient. Inhibitors or chemicals are added
suspension and will drain readily.
to the oil by the oil refiner to ensure compatibility
(2) Obtain a sample of the drained oil and de-
with a range of engines operating under varying
liver it to the base engineer for testing. Drained oil
conditions. The user must observe recommenda-
should be examined for fuel dilution, acidity, and
tions by the engine manufacturer for specific types
presence of solids and other contaminants. Testing
and grades of oil for optimum engine performance.
helps establish the overall condition of the engine
a. Characteristics. Engine lubrication requires
and approximate frequency of need for oil changes.
selection of the proper oil. Refer to the engine man-
(3) Observe the viscosity of drained oil. In die-
ufacturer instructions. Examples of required oil
sel engines oil viscosity increases during service due
characteristics are as follows:
to the gradual oxidation of the oil. Viscosity de-
(1) Oil should h ave sufficient viscosity to pre-
creases if fuel gets into the oil by passing the piston
rings or through leaks.
vent metal-to-metal contact. Oils with lower SAE
e. Oil analysis program.
numbers are lighter and flow more readily than oils
(1) Personnel in the engineer's office, and other
with higher numbers. Heavier oils, those with
cognizant personnel, should refer to the Army Oil
higher SAE numbers, may cause sluggish operation
Analysis Program (AOAP) for sampling and analy-
and power loss.
sis information. The program is described in
(2) Oil should remain stable during use under
changing temperatures and conditions for satisfac-
(2) The an a1ysis of periodic samples of the lu-
bricating oil should report the character and
(3) Check th e engine periodically, such as every
amount of contaminants, wear metals and additives
six months, for accumulation of sludge in the engine
in the oil. However, some amounts of wear metals
filters and strainers and around valve springs. Re-
and contaminants will have been collected by the
fer to the engine manufacturer's literature for spe-
chip collectors, strainers, filters, separators of the
system and also as sludge. To secure the total pic-
(4) Oil must be free of water and sediment.
ture it is necessary to analyze all such collected
Collect a sample of oil in a glass jar. Allow the
material to determine the total rate of
sample to settle. Water and solid contaminants
increase/decrease of each. This will indicate what
settle to the bottom of the jar.
has occurred during the period between samples.
b. Additives. Straight mineral oil does not have
(3) The prudent responsible operator will log
detergent qualities. Therefore, various compounds
and use all such data to track trends that give
are added to the oil. These additives keep the en-
warning of conditions that may result, if uncor-
gine clean by controlling varnish formation or re-
rected, in major problems.
sisting chemical changes to reduce oxidation. Other
additives form a protective film against corrosive
C-2. Gas turbine oil.
Lubricating oil for gas turbines should comply with
c. Mixing oils. Different refineries may use differ-
Federal Specifications MIL-L-23699 or MIL-L-
ent types of additives or certain characteristics of
the mineral oil may vary. Mixing types of oil may
7808. Oil that complies with the specification can
withstand the high temperatures encountered dur-
change the necessary detergent actions. To obtain
ing engine operation.
maximum benefit from additive type oils do not mix
a. Additives. Various compounds are added to
them with straight mineral oil. Concentrations of
mineral oil to provide the special characteristics
the additives is reduced when detergent oils and
required for use in gas turbines. The user must
straight oils are mixed.