This document discusses how hydraulic fluid viscosity impacts hydraulic system performance and efficiency. It presents research on how higher viscosity index (VI) oils can improve efficiency by expanding the fluid's operating temperature window. The document outlines a study comparing the efficiency of different hydraulic fluids in a piston pump test. Fluids with higher VI delivered better efficiency at high pressure and temperature, with efficiencies up to 40% compared to 35% for lower VI fluids. Higher VI fluids maintain viscosity better at high temperatures, reducing leakage and improving volumetric efficiency.

1. A New Performance Level for
Hydraulic Fluids providing Energy
Savings and Emission Reductions
Dr. Hitoshi Hamaguchi
Dr. Eric Fillod
Degussa, RohMax Oil Additives

2. Presentation Outline
• Hydraulic Fluid Trends
• Viscosity Impact on Performance
• Benefits of High VI Oils
• Low Temperature
• High Temperature
• Effects of Viscosity on Pump Efficiency
• VI Effect
• SSI Effect
• Energy Savings by High VI Hydraulic
Fluid
• Conclusions

3. Claims for Improved Efficiency
of Mobile Equipment
“15 percent better fuel efficiency”

4. Claims for Improved Efficiency
of Mobile Equipment
“Cut your fuel costs by
Up to 30%.”

5. Construction Machinery
Production of Earth Moving Equipment in Japan (2003)
Cranes Off-Road Carrier
Road Machines
2% 1% Hydraulic Excavator
4%
Bulldozer 41%
5%
Wheel Loader
10%
Source: Japan Construction
Machinery Manufacturers
Mini Excavator Association
37%
3m3 Class Wheel Loader 20t Class Hydraulic
Pump Pressure: Excavator
42 MPa Pump Pressure:
35 MPa

6. Trends in Mobile Pump Pressure

7. Hydraulic Fluid Trends
•Higher Pressures
• Mobile equipment now at 300 bar, moving to 450 bar
•Smaller, Lighter Equipment
• Reduced fluid volumes
• Less residence time for cooling
•Higher Fluid Operating Temperatures
• 80 °C common for mobile equipment
• 100+ °C peak temperatures
Improved Fluids are Required
Improved Fluids are Required

8. Viscosity Impact on
Hydraulic Performance
10,000
Cavitation
5,000
Poor Flow to Lubricated Areas
Viscosity, mm2/s
1,000
Sluggish Operation
500
Low Mechanical Efficiency
100
50
Optimum Range
10 Reduced productivity, Overheating
5 High wear, Reduced equipment life
1

9. Viscosity Impact on
Hydraulic Performance
Cavitation Sluggish Operations High Wear
Viscosity

10. Actual vs. Nominal Flow Rate
of Hydraulic Pumps
Qa = Qn - Ql
Qleakage
Qnominal
Qactual Qactual
Volumetric
Pump

11. Effect of Viscosity
on Pump Performance
Poor volumetric efficiency
Volumetric Efficiency ηVol.
ηOverall = ηVol. ⋅ ηMech.
Efficiency
Mec
hani
cal E
ffi c ie n
cy η
Optimum Operating Over Mec
all E h.
Range fficie
nc yη
OV
Viscosity High frictional losses

12. High VI Fluids Expand
the Temp. Operating Window
Viscosity
TOW low VI oil
Viscosity
Max.
Viscosity
Min.
TOW high VI oil
40 °C Temperature

13. “In-Service” Viscosity
Seen by the Pump
Fresh oil viscosity
Permanent
Used oil viscosity
Viscosity Temporary
“In-service” viscosity
Base oil viscosity
I
1 to 10 hours Test time

14. Dependence of Efficiency
on “In-Service” Viscosity
100
• The Poiseuille Law
predicts Leakage:
Pressure
QLeak. = const. ⋅
Volumetric Efficiency ηV, %
90 " Viscosity"
• Either HTHS viscosity or
80
viscosity after sonic shear
(ASTM D 5621) at 100 °C
can be used.
70
, overall
60
Multigrade (HV) Oils
At hig h temperatures
s mainly on
50
Monograde (HM) Oils
! efficiency depend
“in-service” vis
cosity.
0 0,2 0,4 0,6 0,8 1 1,2
Pressure / (Nom. Flow · "High Shear" Kin. Viscosity)

15. Studies in a Komatsu HPV35+35
Dual Piston Pump
Komatsu • Pump is driven by a 22 kW
HPV35+35
Piston Pump
electric motor at 1700 rpm.
RohMax Pump
• Both monograde (HM) and
Test Stand multigrade (HV) fluids have
been evaluated at pressures of
30, 70, 140, 210, 280 and 350
bars.
• Pump inlet temperature from
60 to 100°C
• Flow rate, pressure, torque and
rotational speed are measured
Piston Pump
continuously in order to
calculate overall efficiency.

16. Fluids Tested in the Komatsu
HVP35+35 Dual Piston Pump
After 40min Sonic Test
Fresh Oil
(ASTM D 5621)
VI Improver KV40 KV100 VI KV100 %KV100 Losses
ISO 46 VI 100 - 44.98 6.81 105 - -
ISO 46 VI 120 A 44.69 7.20 122 6.87 4.7
ISO 46 VI 140 B 46.08 7.89 141 7.18 8.9
ISO 46 VI 160 C 47.75 8.57 158 7.79 9.0
ISO 46 VI 200 D 46.01 9.66 202 9.01 6.7
ISO 46 VI 160 E 45.99 8.40 160 7.85 6.5
ISO 46 VI 160 F 45.16 8.33 162 7.13 14.5
• Seven mineral oil based fluids, all falling in the ISO 46 viscosity grade.
• One monograde (HM) fluid and six different high VI multigrade fluids (HV)
• Four fluids blended with PAMA-VI improvers to a VI of 120, 140, 160 and
200, all having a comparable viscosity loss after sonic shear.
• The other fluids were blended to meet the same VI of 160 with PAMA-VI
improvers of different levels of shear stability.

17. Dependence of Efficiency
on Viscosity Index
40
VII D
VII C
Overall Efficiency, %
35
• Efficiencies delivered by
different fluids at 350 bars
VII B and 100°C were compared.
30
• Even shear-stable
VII A multigrade fluids suffer from
shear-thinning.
25 • The benefits of high VI fluids
100 120 140 160 180 200 220
over-compensate this effect
Viscosity Index
only at VIs above 140.

18. Performance Claims at High Temperature
VI Effect
Effect of Temperature on Efficiency at 350 bars in Komatsu Piston
Pump
Reference - ISO 46, VI=100
9
A VI of 160 is needed
to obtain significant
% Gain in Global Efficiency
6
efficiency gains
at high temperature
3 Fresh VI
200
160
0 140
120
-3
-6
60 70 80 90 100
Temperature, °C

19. Efficiency Improvements
Depend on Shear Stability
• As shown before, shear-
stable HV fluids deliver
increased pump efficiency.
• In contrast, the fluid
formulated with shear-
unstable polymer F does not
provide high benefits.
VII E VII C VII F

20. Proposed
Performance Level Definition

21. MEHF Field Test
•Caterpillar 318CL Excavator
• 1 m3/~2 ton bucket capacity,
medium size in Cat excavator line
• Cat 3066T diesel engine
• 125hp/93kW
• 2200 rpm max.
• 19-23 l/h fuel consumption
• Dual piston pump feeding 3 piston
motors, plus boom, stick, and bucket
cylinders (345 bar max.)
• Maximum pump flowrates
• 95 l/min per pump
• 190 l/min to system
• Hydraulic fluid volume
• 255 L total in system
• 127 L in tank

22. MEHF Field Test Details
•Test Protocol
• Standard earthmoving work protocol, shifting piles of earth 30 m.
• Mild Fall ambient operating temperatures (7-18°C)
• Equivalent time and work output for each fluid, ~1 minute/work cycle
• Tests conducted with engine at full throttle and 90% throttle
• Test Schedule
• Day 1 – REO 10W @ 90% Throttle
• Day 2 – REO 10W @ Full Throttle
• Day 3 – Oil and Filter Change
• Day 4 – MEHF @ Full Throttle
• Day 5 – MEHF @ Full Throttle
• Day 6 – MEHF @ 90% Throttle
• Day 7 – Oil Change
• Day 8 – REO 10W @ Full Throttle
• Day 9 – REO 10W @ 90% Throttle

23. Work Cycle
1. Take full 2. Rotate 180°,
scoop of dirt travel 30 m
4. Rotate 180°,
3. Dump load return to start

24. MEHF Field Test Details
•Test Fluids
• Baseline established with standard 10W monograde hydraulic
fluid (REO 10W)
• KV 40 = 38.0 cSt, VI = 104
• Comparison made with MEHF 46,
VI fresh = 200
• Used Oil After Shear
KV 40 = 45.8 cSt, VI = 179
• MEHF formulated with RohMax Dynavis® additive system
• VISCOPLEX® 8-219

25. MEHF Field Test Results
Fuel Overall Fuel Fuel Work Cycles Work Cycles
Consumed per Improvement, Consumed per Consumption per Hour, Improvement,
work cycle, Percent Hour, Improvement, Cycles/hour Percent
kg/cycle kg/hour Percent
REO 10W
@ 0.364 --- 19.50 --- 53.5 ---
Full Throttle
REO 10W
@ 0.380 --- 15.20 --- 40.0 ---
90% Throttle
MEHF 46
@ 0.297 + 18.4% 16.80 + 13.8% 56.6 + 5.8%
Full Throttle
MEHF 46
@ 0.280 + 26.3% 13.89 + 8.6% 49.7 + 24.3%
90%Throttle

26. Summary and Conclusion
• Hydraulic Fluid Trends
• Hydraulic system plays important role in the construction machinery
• Higher pump pressure is employed in modern equipment
• Laboratory Studies
• High VI hydraulic fluids formulated with shear-stable viscosity index
improvers provide higher “in-service” viscosity at high operating
temperature and lower viscosity at low start-up temperature.
• We have shown that these fluids will thus help to significantly
improve pump efficiency at both low and high temperature.
• Based on our studies, a new performance level definition for
hydraulic fluids called “Maximum Efficiency Hydraulic Fluid” (MEHF)
has been defined.

27. Summary and Conclusion (cont.)
• MEHF Field Test
• Test compared OEM recommended 10W (L46-46) monograde
with highly shear stable MEHF 46 fluid
• MEHF 46 shows exceptional results in field testing
• Significantly lower fuel consumption
• Increased work output
• Results fit with lab bench tests and theoretical models
• Overall Conclusion
• MEHF provides energy savings and emission reductions