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The Effects of Fuel Dilution with Biodiesel on Lubricant Acidity, Oxidation and Corrosion –
a
Study with CJ-4 and CI-4 PLUS Lubricants
Simon A.G. Watson and Victor W. WongSloan Automotive Laboratory
Massachusetts Institute of Technology
Sloan Automotive Laboratory
2008 Diesel Engine-Efficiency and Emissions Research (DEER) ConferenceAugust 7th, 2008
Sources of Lubricant Contamination
Sloan Automotive Laboratory
•
The combustion chamber is the source of most oil contaminants
Fuel Dilution Concerns for 2007+ Engines and Lubricants
Sloan Automotive Laboratory
•
The aftertreatment regeneration strategy in some engines increases opportunity for fuel to mix with lubricant
•
Interest in the widespread use of Biodiesel fuel
•
Known concerns with biodiesel fuel:–
Poor oxidation stability in storage–
Acidic attack on fuel system components–
Viscosity increase due to polymerization of fuel molecules–
Distillation characteristics lead to higher fuel dilution levels–
Polar methyl ester may interfere with ZDDP effectiveness
Experimental Objectives
Sloan Automotive Laboratory
1.
Investigate the effects of fuel dilution with biodiesel on lubricant degradation and corrosion of engine components
2.
Examine the relative effectiveness of CJ-4 (low ash) and CI-4+ lubricants in protecting components from fuel-borne acids and corrosion
Test Method
Sloan Automotive Laboratory
•
Bench-scale oxidation test based on ASTM D6594
•
Mixtures of fuel and oil heated at 135oC for 160hrs
•
Stressed lubricant analyzed for degradation
•
Corrosion of metal specimens examined
Corrosion Test Specimens
Sloan Automotive Laboratory
•
Copper, tin and lead specimens simulate engine bearings
•
Prepared prior to each test by:–
Polishing surfaces to remove oxide layers
–
Washing in acetone to rinse away metallic dust
•
Corrosion quantified by measuring metallic concentrations in the oil with ICP
Copper
Lead
Tin
25 mm
25 mm
Test Matrix
Sloan Automotive Laboratory
•
Two lubricants were used:-
CJ-4 (Low Ash)-
CI-4+
•
Examined 14 cases: -
0%, 5% and 10% by mass of fuel mixed with oil
-
Diluted with ULSD, B-20 and B-100
•
Six 0% fuel dilution cases also used as controls
LubricantFuel Dilution CJ-4 CI-4+0% X X
5% ULSD X X
10% ULSD X X
5% B-20 X X
10% B-20 X X
5% B-100 X X
10% B-100 X X
Controls3x 0% Fuel Dilution CJ-43x 0% Fuel Dilution CI-4+
Fuel and Lubricant Properties
Sloan Automotive Laboratory
Property Value Limit (D6751)
Type Soy Methyl Ester (SME)TAN [D664] 0.22 0.5
API Service CJ-4 CI-4+API Gravity 29.1 28.9
Viscosity @ 40°C [cSt] 125 146
Viscosity @100°C [cSt] 15.7 14.9
Sulfated Ash (D874) [%] 1.0 1.35
TBN (D2896) [mg KOH/g] 9.6 10.2
Biodiesel Properties:
Lubricant Properties:
0
5
10
15
20
0% 5% ULSD 10% ULSD 5% B-20 10% B-20 5% B-100 10% B-100
Mas
s Lo
ss [%
]
CJ-4CI-4+
Mass Loss Due to Evaporation
Sloan Automotive Laboratory
•
Reduced mass loss is seen in the B-100 cases due to the higher B-
100 boiling point•
Higher fuel dilution levels are expected in engines fueled with biodiesel
Increase in Acidity
Sloan Automotive Laboratory
•
Fuel dilution with B-100 significantly increases the acidity of the stressed lubricants
•
TAN increases at a faster rate in the CJ-4 lubricant
0153045607590
105120135150165180
0% 5% ULSD 10% ULSD 5% B-20 10% B-20 5% B-100 10% B-100
% In
crea
se o
f TA
N a
t 160
hou
rs
CJ-4CI-4+
Total Base Number Retention
Sloan Automotive Laboratory
•
Fuel dilution with B-100 results in higher TBN depletion for both lubricants
0
1
2
3
4
5
6
7
0% 5% ULSD 10% ULSD 5% B-20 10% B-20 5% B-100 10% B-100
TBN
at 1
60 h
ours
[mgK
OH
/g]
CJ-4 (D4739)CI-4+ (D4739)CJ-4 (D5984)CI-4+ (D5984)
Percent Reduction in TBN
Sloan Automotive Laboratory
•
Accounting for different initial TBN levels, fuel dilution with biodiesel only slightly increases TBN depletion
•
The rate of TBN depletion is similar for the CJ-4 and CI-4+ lubricants
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
0% 5% ULSD 10% ULSD 5% B-20 10% B-20 5% B-100 10% B-100
% R
educ
tion
of T
BN
at 1
60 h
ours
CJ-4CI-4+
Viscosity Increase
Sloan Automotive Laboratory
•
Adding fuel to fresh lubricants results in an initial decrease in viscosity
•
Dilution with B-100 significantly increases CJ-4 viscosity at 160 hrs•
Viscosity increase shows similar trends as TAN increase
0
1
2
3
4
5
6
0% 5% ULSD 10% ULSD 5% B-20 10% B-20 5% B-100 10% B-100
Visc
osity
Incr
ease
[mm
2/s]
CJ-4CI-4+
0
1
2
3
4
5
6
7
8
9
10
0 20 40 60 80 100 120 140 160
Time [hours]
TB
N,T
AN
Un
its
[mg
KO
TBN and TAN Crossover
Sloan Automotive Laboratory
•
TAN never exceeds TBN for the cases with no fuel dilution and the cases diluted with only ULSD fuel
CJ-4, 10% ULSD
CI-4+, 10% ULSD
TAN
TBN
0
1
2
3
4
5
6
7
8
9
10
0 20 40 60 80 100 120 140 160
Time [hours]
TB
N,T
AN
Un
its
[mg
KO
TAN and TBN Crossover
Sloan Automotive Laboratory
CJ-4, 10% ULSD
CI-4+, 10% ULSD
CJ-4, 10% B-100
CI-4+, 10% B-100
TAN
TBN
•
Dilution with biodiesel significantly increases the TAN at 160 hours
0
1
2
3
4
5
6
7
8
9
10
0 20 40 60 80 100 120 140 160
Time [hours]
TB
N,T
AN
Un
its
[mg
KO
TBN and TAN Crossover
Sloan Automotive Laboratory
CJ-4, 10% ULSD
CI-4+, 10% ULSD
CJ-4, 10% B-100
CI-4+, 10% B-100
TAN
TBN
CJ-4 CI-4+
•
TAN crosses TBN earlier in the tests with the CJ-4 oil•
This observation alone would seem to indicate that corrosion in the CJ-4 oil will be higher than with CI-4+ oil
Corrosion
Sloan Automotive Laboratory
Copper
Tin
Lead
Unused 5% B-200% 5% ULSD 5% B-100
Increasing Biodiesel Concentration in the CJ-4 Lubricant
Copper Corrosion
Sloan Automotive Laboratory
•
CJ-4 lubricant reduces corrosion of copper in all cases•
Copper corrosion increases substantially in the CI-4+, B-100 cases•
Low to zero levels of tin found in stressed oil
02468
101214161820
0% 5% ULSD 10% ULSD 5% B-20 10% B-20 5% B-100 10% B-100
Mas
s of
Cop
per [
mg]
CJ-4, CuCI-4+, Cu
0
50
100
150
200
250
0% 5% ULSD 10% ULSD 5% B-20 10% B-20 5% B-100 10% B-100
Mas
s of
Lea
d [m
g]
CJ-4, PbCI-4+, Pb
Lead Corrosion
Sloan Automotive Laboratory
•
A 10 times increase in lead corrosion is observed in the B-100 cases•
The CJ-4 lubricant appears to give improved corrosion protection
Conclusions
Sloan Automotive Laboratory
•
Higher fuel dilution levels are expected with biodiesel fuel
•
In this test, fuel dilution appears to reduce TBN retention and ultimately increase viscosity of the stressed oil
•
Dilution with B-100 further decreases TBN and increases TAN, reduces lubricant life and increases viscosity
•
B-100 substantially increases corrosion of lead (10x) and copper in the stressed lubricant
•
Reduced corrosion was observed with the CJ-4 oil, although acidity was increased
•
TBN and TAN crossover was an unreliable indicator of relative lubricant performance
Sloan Automotive Laboratory
•
Caterpillar•
Chevron
•
Ciba Specialty Chemicals•
Cummins
•
Department of Energy
This research is supported by the MIT Consortium to Optimize Lubricants and Diesel Engines for Robust Emission Aftertreatment Systems
•
Komatsu•
Lutek
LLC.
•
Sud-Chemie•
Valvoline
•
Ford
We thank for the following organizations/companies for their support:
Acknowledgements
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