Role of Viscosity Index Improvers in Fuel Efficient Lubricants

1
Role of Viscosity Index Improvers in Fuel
Efficient Lubricants

• Thomas Schimmel
• 2007-11-28

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Outline

• Transmission Fluids
• Hydraulic Fluids
• Outlook

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Fuel efficient transmission fluids

• Modern transmission fluids are formulated at
  lower viscosity to reduce viscous drag.
• For passenger cars viscosity at 20 50 C is
  relevant for governmental consumption tests.
• High Viscosity Index is needed.
• To maintain stay-in-grade classification it is
  necessary to use shear-stable VI Improvers.
• Modern highly efficient transmissions are
  designed towards enhanced torque capacity and
  reduced size.
• Resulting higher operating temperatures have to
  be considered in formulation development.

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SAE J306 has been updated for fuel economy and
shear stability

• Stay-in-grade after shear in KRL 20 hours (CEC
  L-45-A-99)

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Significant Change in SAE 75W-90
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More Shear Stable Viscoplex for SAE 75W-90
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Efficiency of Gear Oils Monograde SAE 90 and
Multigrade SAE 75W-90 based on shear stable PAMA
VII
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Benefits of shear stable SAE 75W-90
SAE 75W-90 SAE 80W-90
Cold Start-Up Temperature(_at_ 150 000 mPas) Cold Start-Up Temperature(_at_ 150 000 mPas)
- 40 C - 26 C
Easy Shiftingtypical 5000 mPas Easy Shiftingtypical 5000 mPas
Down to -20 C Down to -10 C
Gear Efficiency at 75 Nm (average ECE test cycle) Gear Efficiency at 75 Nm (average ECE test cycle)
0 C 0 C
80 70
Average 20 44 C (typical for ECE test cycle) Average 20 44 C (typical for ECE test cycle)
94 91
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Influence of VII and base oil on operating
temperature
T in C
KV 100 13 mm2/s PAO
Mineral Oil
130
125
120
PIB

115
Mineral Oil
110
105
100
PAMA
95
90
85
VW PV 1452
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The Optimum Range of Viscosity for Hydraulic
Fluids
10000
Cavitation
5000
Poor Flow to Lubricated Areas
1000
Sluggish Operation
500
Low Mechanical Efficiency
100
Viscosity, mm2/s
50
Optimum Range
10
Reduced productivity, Overheating
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High wear, Reduced equipment life
1
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High VI Fluids have Extended Operating
Temperatures
10000
Low VI
1000
High VI
100
50
ISO 46
Kinematic Viscosity mm²/s
High VI
10
5.0
Low VI
3.0
-40
-20
0
20
40
60
80
100
120
140
Temperature, C
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Use of Shear Stable VIIs Increases Efficiency
20
Shear stable PAMA(KRL Viscosity Loss 13)
10
Total Efficiency Gain
0
Medium shear stable PAMA(KRL Viscosity Loss 30)
-10
100
80
60
40
20
Temperature C
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Dispersant PAMA VIIs Increase Film Thickness
100
Ball on disc at 80C
Film Thickness nm
10
1
0.001
0.01
0.1
1
10
Speed m/s
Increased film thickness provides better
lubrication at low speed.
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OutlookEffects of higher film thickness

• Classical properties of dispersant PAMA
• Soot and particle dispersancy
• New properties of dispersant PAMA
• Reduced friction at mixed lubrication
• Reduced wear
• Longer pitting lifetime

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Conclusion

• Polymethacrylates add ecological benefits to
  lubricant formulations.
• Multi-grade fluids formulated with shear stable
  PAMA VI Improvers lead to
• higher efficiency
• lower operating temperatures
• PAMA VI Improvers of high shear stability and
  with dispersant function give new options towards
  fuel efficient formulation design.

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