F
OR
M
ODELS
: JGI, JGM, JGN, JGP
AND
JGQ
S
ECTION
4 L
UBRICATION
PAGE 4-2
A lubricant of a proper viscosity helps to cushion shock loads or pulsations to
reduce vibration and noise, and increase component life.
Lubricant Characteristics
Viscosity
Viscosity is a measurement of the resistance of a fluid to flow. Viscosity measurement is
temperature dependent and decreases with increasing temperature. Most commonly used
are units of dynamic viscosity, which is expressed in units of Saybolt Universal Seconds
(SUS) in English units and by centistoke (cSt) in metric. Proper viscosity is the most impor-
tant aspect of compressor lubrication. The chart below illustrates the viscosity differences
between base stock types.
Oil viscosity will increase when the oil begins to oxidize or when it is contaminated with oil or
another liquid with higher viscosity. Oil viscosity will decrease when it is contaminated with
hydrocarbon gas condensate or another liquid with lower viscosity. Oil will not "break-down"
10
20
30
40
50
60
70
80
90
100
110
120
130
140
4.0
5.0
6.0
7.0
8.0
20
9.0
10
15
40
30
75
50
150
100
300
200
400
500
5000
3000
2000
1000
10000
4.0
5.0
6.0
7.0
8.0
20
9.0
10
15
40
30
75
50
150
100
300
200
400
500
5000
3000
2000
1000
10000
Temperature, Degrees Celsius (°C)
Kinematic V
iscosit
y
, Centistoke
(cS
t)
VISCOSITY INDEX:
1. PAG = > 200 (Synthetic)
2. PAO = approx. 150 (Synthetic)
3. Paraffinic Mineral Oil = approx. 100
4. Diester = approx. 70 (Synthetic)
5. Napthenic Mineral Oil = < 80
Note: Curves are based on specific oils.
1.
3.
4.
5.
2.
F
IGURE
4-1 V
ISCOSITY
VS
. T
EMPERATURE
G
RAPH
S
HOWING
D
IFFERENT
T
YPES
OF
L
UBRICANTS
