A Prototype Low-Viscosity Engine Oil Using an
Ionic Liquid as Anti-Wear Additive
J. Qu, H. Luo, S. Dai, P.J. Blau, T.J. Toops, J.M. Storey, B.H. West
Oak Ridge National laboratory
Michael B. Viola, Tasfia Ahmed, *Donald Smolenski, *Gregory Mordukhovich
General Motors
GM Powertrain Fuels, Fluids, Lubricants and Materials Labs
E.A. Bardasz, Scott Halfhill, Joe Tomaro
The Lubrizol Company
Research sponsored by the Vehicle Technologies Program,
Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy.
*Former GM R&D Employees
Motivation and Approach for Engine Tribology Research
Motivation
● Of the energy output of fuel in a car engine, 33% is spent in exhaust,
29% in cooling and 38% in mechanical energy, of which friction losses
account for 33% and air resistance for 5%1
Approaches
● Improved engine design
● Advanced engine materials and surface engineering
● More effective engine lubricants
– Lower cost, easier implementation, and usually backward
compatible
DOE’s goal of 2% increase in engine fuel efficiency via lubricant advances
1) VTT Technical Research Centre of Finland and Argonne National Laboratory (ANL) Science News January 12, 2012
Ionic liquids as Oil Additives
• Enhanced wear protection by ionic liquid additives
– Enable the use of lower viscosity oils resulting in improved fuel economy
Wear Increase
Stribeck Curve
BL
ML
EHL
Oil
Oil + IL
= viscosity
N = speed
P = load
F = COF
Ionic liquids lubrication
• ILs as neat lubricants or base stocks
oC)
– High thermal stability (up to 500
– High viscosity index (120-370)
– Low EHL/ML friction due to low
pressure-viscosity coefficient
– Wear protection by tribo-film formation
– Suitable for specialty bearing
components
• ILs as oil additives
– Potential multi-functions: AW/EP, FM,
corrosion inhibitor, detergent
– Ashless low sludge
– Allow the use of lower viscosity oils
– Advantage: cost effective and easier to
penetrate into the lubricant market
– Problem: most ILs insoluble in oils
Ionic liquids are ‘room temperature molten salts’, composed of cations &
anions
5
4
3
N
+
2
N
R1
1
+
N
R
1-alkyl-3-methylimidazolium
R
N-alkylpyridinium
R2
+
N
R
4
R3
Tetraalkylammonium
Common Cations
[PF6][(CF3SO2)2N]- (Tf2N)
[(C2F5SO2)2N]- (BETI)
[BF4][CF3SO3]-
[BR1R2R3R4][P(O)2(OR)2]− (phosphate)
[P(O)2(R)2]− (phosphinate)
Common Anions
R1 + R4
P
R2
R3
Tetraalkylphosphonium
(R1,2,3,4 = alkyl)
[CH3CO2][CF3CO2]-, [NO3]Br-, Cl-, I[Al2Cl7]-, [AlCl4]- (decom
Breakthrough in oil-miscible ionic liquids
Most ILs have very limited oil-solubility (<<1%).
(ORNL just hired a grad student to check their hypothesis)
Molecular design hypothesis: 3D quaternary ion structures
w/ long hydrocarbon chains to dilute the charge to be
compatible with neutral oil molecules Examples of oilmiscible ILs:
PAO(50%) 10W(50%)
+
+
IL18 (50%) IL18 (50%)
● [P66614][DTMPP] (IL16) (precipitated slightly in FF oils)
● [P66614][DEHP] (IL18)
IL18: trihexyltetradecylphosphonium bis(2-ethylhexyl) phosphate
CH3(CH2)7
+
N
CH3(CH2)7
H
O
CF3 S N S CF3
(CH2)7CH3
H3C(H2C)5
(CH2)5CH3
(CH2)5CH3
(CH2)13CH3
P
H3C(H2C)5
OCH2CH2CH2CH3
O
(CH2)5CH3
(CH2)5CH3
O
-
O
H3C(H2C)5
(CH2)5CH3
(CH2)5CH3
CH2CH(CH3)CH2C(CH3)3
[P66614][DEHP] (IL18)
OCH2CH(C2H5)CH2CH2CH2CH3
O
P
OCH2CH2CH2CH3
P
(CH2)13CH3
IL20
P
-
CH2CH(CH3)CH2C(CH3)3
O
P
O
O
[P66614][DTMPP] (IL16)
(CH2)13CH3
O
Confirming
miscibility
P
-
O
OCH2CH(C2H5)CH2CH2CH2CH3
B. Yu, and J. Qu*, et al., Wear (2012) 289 (2012) 58.
J. Qu, et al., ACS Applied Materials & Interfaces 4 (2) (2012) 997.
IL18 more effective in anti-scuffing than ZDDP at 100 oC
ZDDP: Zinc dialkyldithiophosphates
Current AW technology
Friction coefficient
0.3
0.25
Scuffed!
PAO+1% ZDDP
0.2
PAO+1% IL18
0.15
• Oil viscosity is low at 100 oC: 4 cSt (35 cSt at
RT)
• While 1% ZDDP could not provide sufficient
scuffing protection, 1% IL18 worked nicely.
0.1
0.05
0
4
40
400
Sliding distance (m)
Wear rate (mm3/N-m)
1.E-04
Ring
4000
Mo-coated piston ring
Grey cast iron cylinder liner
Liner
1.E-05
1.E-06
1.E-07
1.E-08
Plint TE77 High Frequency
Tribometer
PAO+1% ZDDP
PAO+1% IL18
J. Qu, et al., Tribology International (accepted)
Prototype IL-additized engine oil
First prototype fully-formulated automotive engine oil
using PAO 4 cSt as the base oil and 1.0 wt.%
[P66614][DEHP] (IL18) as AW has been formulated
and produced by Lubrizol.
5 gallons of
prototype
engine oil
using IL18
as AW
Ultra-low viscosity, comparable to the proposed SAE
8 grade.
Mobil 1TM 5W-30 engine oil
Mobil CleanTM 5W-30 oil
SAE XW-20 engine oil
SAE XW-16 (newest)
proposed SAE XW-12
proposed SAE XW-8
IL-additized engine oil
cSt @ 40 oC
64.27
56.1
cSt @ 100 oC
11.38
10.1
>6.9, <9.3
>6.1, <8.2
25.53
5.38
HTHS (cP @150 oC)
3.11
3.06
>2.6
>2.3
>2.0
>1.7
1.85
Superior Friction/Wear Behavior of the Prototype
IL-18 Additized Engine Oil
Rolling-sliding bench tests on MTM2 Mini-Traction Machine
33% friction reduction in ML/EHL and 92% wear reduction in BL compared to
Mobil Clean 5W-30 engine oil.
20% friction reduction in ML/EHL and 38% wear reduction in BL compared to
Mobil 1TM 5W-30 engine oil.
20-33% friction
reduction in ML/EHL
0.06
Wear Rate (mm3/sec)
Friction Coefficient
0.07
0.05
BL
0.04
0.03
ML
0.02
Mobil Clean 5W30
Mobil 1 5W30
Fully-formulated w/ 1% IL18
0.01
0
50
EHL
500
Rolling Speed (mm/s, log scale)
5000
2.0E-06
1.8E-06
1.6E-06
1.4E-06
1.2E-06
1.0E-06
8.0E-07
6.0E-07
4.0E-07
2.0E-07
0.0E+00
1.5E-06
38-92% wear
reduction in BL
Mobil Clean
5W30
Mobil 1
5W30
1.7E-07
Fullyformulated w/
1%IL18
1.1E-07
High Temperature High Load (HTHL) Engine Test
LSX Engine:
Performance Parts 6.2L Gen4 small block engine
Bore X Stroke
4.065” X 3.622”
Compression
9.0:1
Block
Cast Iron
Cylinder Heads
Cast Aluminum
Power
450 HP
Torque
444 ft-lbs
LSX Engine Setup in Test Cell #14
Test run at conditions for 100 hours
Speed: 2700 RPM
Load: 120 N
Coolant out Temperature:120ºC
Oil sump temperature: 145ºC
Oil samples taken at: fresh, 20, 40, 60, 80 and 100 hours
HTHL Results
Kinematic 40C
Kinematic 100C
12
70
Mobil 1
Mobil 1
10
50
Kinematic Viscosity (cSt)
Kinematic Viscosity (cSt)
Il 18
IL 18
60
40
30
20
8
6
4
2
10
0
0
0
20
40
60
80
0
100
20
40
30
HTHL Mobil 1 Testing Elements by Inductively Coupled Plasma Atomic
Emissions Spectrometry (ICP-AES)
Fe
Al
Cu
30
80
100
HTHL IL 18 Testing Elements by Inductively Coupled Plasma Atomic
Emissions Spectrometry (ICP-AES)
Fe
Si
25
25
20
20
Elements (mg/kg)
Elements (mg/kg)
60
Test Hours
Test Hours
15
Al
Cu
Si
15
10
10
5
5
0
0
0
20
40
60
Test Hours
80
100
0
20
40
60
Test Hours
80
100
HTHL Results Continued
Oil used on 100 hour HTHL test
● Mobil 1 5W-30 41.9 oz
● additized IL18 41.2 oz
Oil
HTHS New
HTHS 100 Hours
Mobil 1
3.11 cP
3.17
FF IL18
1.85 cP
2.03
Working on two new
oil classifications:
HTHS at 150C
Grade 8 1.7
Grade 12 2.0
• Engine wear and oil aging
performance comparable
to that of Mobil 1TM 5W-30
engine oil
• IL18 provides adequate
wear protection at such a
low oil viscosity
Sequence VID Fuel Economy Test Results
Sequence VID fuel efficiency engine dyno
tests with the prototype IL-18 additized engine
oil
Fuel economy 3.93% higher than the
baseline (20W-30)
Fuel economy 2.01% higher than the
Mobil 1TM 5W-30 engine oil
Reduction of 81 gCO2 on FTP
Improved fuel economy over
baseline engine oil (%)
This test measures the fuel economy of
engine oils on a GM 3.6L HF V6 engine at six
steady state operations at 16 and 100 hours
of operation
5
4.18
4
3.68
3
2
1.92
1
0
Moil 1 5W-30 IL-additized oil IL-additized oil
(run 1)
(run 2)
IL-18 compatibility with TWCs evaluated
Catalyst core for
engine aging
FUL-TWC
Loaded into exhaust can, ready for
aging using a gasoline genset
Close-coupled TWC from GM:
aged to full useful life (FUL)
equivalent (150K miles) using
accelerated techniques
•
•
Lubricant additives
included in the fuel
Amount (35 g*) based
on average lifetime oil
consumption
Three runs
− IL-18
− ZDDP
− No Additive (NA)
Gas Genset
3500W Briggs&Stratton
~250cc, 3600 rpm, AFR ~12
*B.H. West and C.S. Sluder, SAE 2013-01-0884.
UEGO
sensor
TWC
•
TC
Gas
sampling
port
Gas
sampling
port
TC
Make-up air to
control AFR at
catalyst inlet
Engine aging:
1. Switch between
rich and lean to
avoid high catalyst
temperatures
2. 8 gallons gasoline
consumed within
25 hours
3. Tinlet < 900C
Aged catalysts evaluated using flow bench reactors
Aged catalyst core
Small aged
catalyst core
Catalyst loaded into
quartz tube reactor
500 oC
100 oC
Gas flow: 0.1% C3H6, 1.8% CO,
0.12% NO, 0.159% O2, 0.6% H2, 5%
H2O, 5% CO, and balance N2
SV = 74000 hr-1
bench reactor
TWC inlet evaluated to measure impact of additives
Difference
between FUL+NA
and FUL is minor
for all 3 gases
ZDDP-aged TWC
shows the
highest
deactivation
IL18 shows less
impact than
ZDDP
C3H6: propene, also known as propylene
IL-18 has moderately less impact TWC than ZDDP
For the IL-18 aged TWCs (FUL + IL) the 50% conversion temperatures (T50) are less
than ZDDP-aged TWCS (FUL + ZDDP) for each gas
T50 is closer to FUL + NA than FUL + ZDDP for the FUL + IL
200
FUL
FUL + NA
FUL + ZDDP
FUL + IL
250
FUL
FUL + No additive(NA)
150
FUL + ZDDP
100
FUL + IL
228
247
268
257
227
246
266
255
50
225
247
272
241
T50 Light-off temp. (oC)
300
NO
C3H6
CO
0
Conclusions
Have successfully created a fully formulated IL engine oil
Demonstrated successful wear and friction performance of IL formulation
on bench and engine testing
The IL18 formulation resulted in a 2.01% fuel economy improvement
compared to Mobil 1 5W-30 on Sequence VID testing
Next Steps
Submitted DOE FOA proposal on next generation of IL for engine oil
Optimize IL18 formulation to obtain HTHS of 2.0 cP and conduct HTHL
engine testing
Conduct Sequence IIIG engine wear and Sequence VID fuel economy
testing
Work to incorporate IL18 fuel economy benefit into future dexosTM fuel
economy requirements
Acknowledgements
DOE VTO Fuels and Lubricants Program and GM R&D Center for funding support
DOE HQ program managers Kevin Stork and Steve Przesmitzki, ORNL program managers
Ron Graves and Robert Wagner, and GM manager Eric Schneider for strong support to do
this research
ORNL team
●
Co-PIs: Peter Blau (retired), Huimin Luo, Sheng Dai, Bruce Bunting (retired), Brian West
●
Key technical personnel: Todd Toops, Jane Howe (left ORNL), Harry Meyer III, Miaofang Chi,
Donovan Leonard, John Storey, Samuel Lewis Sr.
●
Postdocs/students: Bo Yu (left ORNL), William Barnhill, Chao Xie, Cheng Ma, and Dinesh Bansal
(left ORNL)
GM team:
●
PIs: Michael Viola, Donald Smolenski (retired), Gregory Mordukhovich (formerly with GM),
Changsoo Kim, and Simon Tung (retired)
●
Key technical personnel: Tasfia Ahmed, Meryn D’Silva, Paul Harvath, and Ngoc-Ha Nguyen
Thank You
Backup
MTM2 Testing
Tests conducted in this study were done
on a Mini Traction Machine (MTM-2)
Disc specification:
Material - AISI52100 steel
Surface hardness 62.5 Rc
Average roughness 0.01 µm Ra
Average asperities slope angle 0.1º λ
Initial Contact is at 42 mm diameter
Ball specification:
19.5 mm diameter
Material - AISI52100 steel
Surface hardness 64 Rc
Average roughness 0.025 µm Ra
Average asperities slope angle 3.5º λ
Sample Set up on Mini Traction Machine -2
Mini Traction Machine-2
Stribeck Curve Tests Parameters to measure (COF):
Speed :
100 mms-1 to 3200 mms-1
Load:
75 N
Sliding Rolling Ratio:
50%
Temperature:
100ºC
Step Size:
100 mms-1
Step time:
6 sec
Lube amount:
40 mL
Durability Tests Parameters to measure wear
Speed :
20 mms-1
Load:
75 N
Sliding Rolling Ratio:
95%
Temperature:
100ºC
Lube amount:
40 mL
Duration:
15 hours standard
Wear rate data was obtained using Zygo Profilometer
Why IL performed better than ZDDP?
– a hypothesis
Before contact and rubbing…compared neutral ZDDP molecules, ionic liquids tend to absorb to the metal surface to possibly provide
a higher localized concentration at the contact interface…
Ring
Ring
-
-
+
+
+
Ionic liquid in oil
ZDDP in oil
+
Liner
-
+
-
Line
r
• In contact and rubbing…ionic liquids react with wear debris and metal surface to form an anti-wear tribo-film…
Anti-wear tribo-film
Metal surface