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Diesel Engines Showing Excellent Performance and Durability with Reduced TBN Lubricants and Low Sulfur Fuel

Diesel Engines Showing Excellent Performance and Durability with Reduced TBN Lubricants and Low Sulfur Fuel. Patrice Estoueig 3 rd International Conference 'Lubricants Russia 2007'. Moscow November, 29 th 2007. The Changing Requirement for TBN.

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Diesel Engines Showing Excellent Performance and Durability with Reduced TBN Lubricants and Low Sulfur Fuel

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  1. Diesel Engines Showing Excellent Performance and Durability with Reduced TBN Lubricants and Low Sulfur Fuel Patrice Estoueig 3rd International Conference 'Lubricants Russia 2007'. Moscow November, 29th 2007

  2. The Changing Requirement for TBN • TBN is a measure of a lubricant’s base reserve used for neutralizing acids • Partly “strong base” which neutralizes acids very effectively • Partly “weak base” which is less effective in neutralizing acids • SAE 972950 shows detergent chemistry impacts • Over the last 3 decades the nature of acidic contaminants has shifted • Historically more strong acids (H2SO4) from combustion of high sulfur fuel • More acids and lower temperatures • Drain periods TBN limited and not long enough to experience high oxidation • Now mostly weak acids from oxidation of base oils • Less acids as contaminants and vastly increased temperatures • Longer drains resulting in more oxidative exposure

  3. The Introduction of Chemical Limits for Lubricants • With ever more stringent emission legislation, OEMs introduced exhaust gas after-treatment devices • These devices were anticipated to be sensitive to sulfated ash, sulfur, and phosphorus in fuels and lubricants • Chemical restrictions were imposed • Diesel fuel sulfur limited to a maximum of 15 mg/kg • Diesel engine lubricants limited to • Maximum 1.0 % sulfated ash (less detergent) • Maximum 0.12 % phosphorus (less ZnDTP anti-wear) • Maximum 0.4 % sulfur • These chemical restrictions result in lower TBN lubricants

  4. A Field Test to Study Lubricant Degradation • Objectives: • Evaluate the impact of chemical restrictions on lubricant degradation • Comparison of CI-4 Plus and CJ-4 type lubricants • Evaluate the impact of lower sulfur diesel fuel on lubricant degradation • Comparison of regular and ultra-low sulfur diesel fuel • Field test description • Test truck fleet doing Delivery Service • Ten units total • Five units on regular sulfur diesel fuel (RSD) • Five units on ultra-low sulfur diesel fuel (ULSD) • Flush-and-run type operation • Drain interval nominally 25,000 miles with intermediate samples

  5. Test Oil Description

  6. CJ-4 Oils Have Lower TBN Due to SAPS Limitations TBN D4739, mg KOH/g

  7. Used Oil Lead Shows No Correlation with Fresh Oil or Used Oil TBN

  8. TBN or TAN Based Used Oil Rejection Limits Do Not Apply to Modern Engines Using Low S Fuel and CJ-4 Oils

  9. Engines on Low S Fuel Showing Lower Used Oil Iron Content ; Less Wear ?

  10. Statistical Analysis Confirms the Significant Difference in Used Oil Iron

  11. Search for the Source of the Used Oil Fe Difference • Engine inspections were performed on two of the units • Both ran on the CI-4 Plus oil for the full duration of the field test • One used ULSD, the other RSD • Units had very similar mileage (165,000 and 170,000) • Inspected parts • Valve train • Bearings • Ring and liners

  12. No Difference in Valve Train Wear Between RSD and ULSD Units Crossheads from RSD Unit Crossheads from ULSD Unit

  13. No Obvious Difference in Bearing Wear Between RSD and ULSD Units Bearings from RSD Unit Bearings from ULSD Unit

  14. ULSD Liner Shows Less Wear Anti-Thrust Side Indicator Liner Wear Step Polished Area below Top Ring Reversal Point Liner from RSD Unit Liner from ULSD Unit

  15. ULSD Unit Shows Consistently Lower Liner Wear

  16. Microscopic Images from RSD and ULSD Liners Show Difference in Wear Liner from RSD Unit Liner from ULSD Unit

  17. Liner Wear, with RSD, Has Corrosive Component : Crevice Corrosion – Crack Formation – Crack Propagation - Spalling Exposed Graphite Flake Void from Removal of Cast Iron Propagating Cracks Liner from RSD Unit

  18. Conclusions • Properly formulated low TBN CJ-4 oils provide excellent engine performance • TBN is not a clear indicator of fresh or used lubricant quality • Chemical limits in CJ-4 allow for the formulation of diesel engine lubricants with performance equal to conventional CI-4 Plus lubricants, thus maintaining backward compatibility • Further reduction of sulfur and phosphorus levels could significantly impact lubricant performance to the point that backward compatibility can no longer be maintained • Low sulfur diesel fuel reduces acid formation in the power cylinder and improves the durability of diesel engines

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