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

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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. Wong Sloan Automotive Laboratory Massachusetts Institute of Technology

2008 Diesel Engine-Efficiency and Emissions Research (DEER) Conference August 7th, 2008

Sloan Automotive Laboratory Sources of Lubricant Contamination • The combustion chamber is the source of most oil contaminants

Sloan Automotive Laboratory Fuel Dilution Concerns for 2007+ Engines and Lubricants

• 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

Sloan Automotive Laboratory Experimental Objectives

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

Sloan Automotive Laboratory Test Method

• Bench-scale oxidation test based on ASTM D6594 • Mixtures of fuel and oil o heated at 135 C for 160hrs • Stressed lubricant analyzed for degradation • Corrosion of metal specimens examined

Sloan Automotive Laboratory Corrosion Test Specimens

• Copper, tin and lead specimens 25 mm simulate engine bearings • Prepared prior to each test by: Copper 25 mm – Polishing surfaces to remove oxide layers

– Washing in acetone to rinse away metallic dust Tin • Corrosion quantified by measuring metallic concentrations in the oil with Lead ICP

Sloan Automotive Laboratory Test Matrix

• Two lubricants were used: Lubricant - CJ-4 (Low Ash) Fuel Dilution CJ-4 CI-4+ - CI-4+ 0% X X 5% ULSD X X • Examined 14 cases: 10% ULSD X X - 0%, 5% and 10% by mass of 5% B-20 X X fuel mixed with oil 10% B-20 X X

- Diluted with ULSD, B-20 and 5% B-100 X X B-100 10% B-100 X X

• Six 0% fuel dilution cases also used as controls Controls 3x 0% Fuel Dilution CJ-4 3x 0% Fuel Dilution CI-4+

Sloan Automotive Laboratory Fuel and Lubricant Properties

Lubricant Properties: 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: Property Value Limit (D6751) Type Soy Methyl Ester (SME) TAN [D664] 0.22 0.5

Sloan Automotive Laboratory Mass Loss Due to Evaporation

CJ-4 20 CI-4+

10 Mass Loss [%] Loss Mass

0 0% 5% ULSD 10% ULSD 5% B-20 10% B-20 5% B-100 10% B-100 • 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

Sloan Automotive Laboratory Increase in Acidity

180 CJ-4 165 CI-4+ 150 135 120 105 90 75 60 45 30

% Increase of TAN at 160 160 hours at TAN of Increase % 15 0 0% 5% ULSD 10% ULSD 5% B-20 10% B-20 5% B-100 10% B-100 • Fuel dilution with B-100 significantly increases the acidity of the stressed lubricants

• TAN increases at a faster rate in the CJ-4 lubricant

Sloan Automotive Laboratory Total Base Number Retention

7 CJ-4 (D4739) CI-4+ (D4739) 6 CJ-4 (D5984) CI-4+ (D5984) 5

2 TBN at 160 hours [mgKOH/g] 160 at TBN 1

0 0% 5% ULSD 10% ULSD 5% B-20 10% B-20 5% B-100 10% B-100 • Fuel dilution with B-100 results in higher TBN depletion for both lubricants

Sloan Automotive Laboratory Percent Reduction in TBN

70.00 CJ-4 60.00 CI-4+

50.00

40.00

30.00

20.00

10.00 % Reduction of% Reduction TBN at 160 hours 0.00 0% 5% ULSD 10% ULSD 5% B-20 10% B-20 5% B-100 10% B-100 • 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

Sloan Automotive Laboratory Viscosity Increase

• 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 6 CJ-4 CI-4+ 5

Viscosity Increase [mm2/s] Increase Viscosity 1

0 0% 5% ULSD 10% ULSD 5% B-20 10% B-20 5% B-100 10% B-100

Sloan Automotive Laboratory TBN and TAN Crossover

10 9 CJ-4, 10% ULSD 8 CI-4+, 10% ULSD TBN 7 6 5 4 TAN 3 2 TBN,TAN Units [mgKO Units TBN,TAN 1 0 0 20 40 60 80 100 120 140 160 Time [hours]

• TAN never exceeds TBN for the cases with no fuel dilution and the cases diluted with only ULSD fuel

Sloan Automotive Laboratory TAN and TBN Crossover

10 9 CJ-4, 10% ULSD 8 CI-4+, 10% ULSD TBN 7 CJ-4, 10% B-100 6 CI-4+, 10% B-100 5 4 TAN 3 2 TBN,TAN Units [mgKO Units TBN,TAN 1 0 0 20 40 60 80 100 120 140 160 Time [hours]

• Dilution with biodiesel significantly increases the TAN at 160 hours

Sloan Automotive Laboratory TBN and TAN Crossover

10 9 CJ-4, 10% ULSD 8 CI-4+, 10% ULSD TBN 7 CJ-4, 10% B-100 6 CI-4+, 10% B-100 5 4 TAN 3 2 TBN,TAN Units [mgKO Units TBN,TAN 1 CJ-4 CI-4+ 0 0 20 40 60 80 100 120 140 160 Time [hours] • 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

Sloan Automotive Laboratory Corrosion Unused 0% 5% ULSD 5% B-20 5% B-100

Copper

Tin

Lead

Increasing Biodiesel Concentration in the CJ-4 Lubricant

Sloan Automotive Laboratory Copper Corrosion

20 CJ-4, Cu 18 CI-4+, Cu 16 14 12 10 8 6

Mass of Mass [mg] of Copper 4 2 0 0% 5% ULSD 10% ULSD 5% B-20 10% B-20 5% B-100 10% B-100 • 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

Sloan Automotive Laboratory Lead Corrosion

250 CJ-4, Pb CI-4+, Pb 200

150

100

Mass of Lead [mg] Lead of Mass 50

0 0% 5% ULSD 10% ULSD 5% B-20 10% B-20 5% B-100 10% B-100 • A 10 times increase in lead corrosion is observed in the B-100 cases • The CJ-4 lubricant appears to give improved corrosion protection

Sloan Automotive Laboratory Conclusions • 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 Acknowledgements This research is supported by the MIT Consortium to Optimize Lubricants and Diesel Engines for Robust Emission Aftertreatment Systems

We thank for the following organizations/companies for their support:

• Caterpillar • Komatsu • Chevron • Lutek LLC. • Ciba Specialty Chemicals • Sud-Chemie • Cummins • Valvoline • Department of Energy • Ford

Sloan Automotive Laboratory