Case Study – Fuel dilution of engine oil

Case Study – Fuel Dilution of Engine Oil in Locomotives


locomtive-crankshaftAfter performing Oil Analysis on locomotives in the rail Industry for many years now, Techenomics International has seen the many benefits and large amount of dollars companies can save, by implementing a preventative maintenance schedule.

It only takes the saving of one or two engine failures to underwrite the cost of the oil analysis programme.

The example outlined in this case study, highlights work Techenomics carried out for an existing client and how their oil analysis programme identified the need for maintenance interventions, preventing engine failure from occurring


A locomotive underwent an engine change following the failure of the number 5 and 6 crankshaft bearings. The oil performance of the engine following its return to service was closely monitored to gather data on the trending of wear materials and engine condition.

Initial oil samples throughout the engines first month of service showed no issues with the oil condition.

Another sample was taken approximately one month after the engine returned to service and showed a significant drop in oil viscosity from 135 down to 103.


Based on our oil analysis results and failure analysis recommendations provided by Techenomics, the client was advised to inspect the engine for fuel leaks. Techenomics advised to take regular oil samples to chart the oil performance.

The locomotive was not immediately recalled to the depot to investigate the potential fuel dilution of the oil. Further oil samples showed that the viscosity continued to drop and reached a low of 86.


Following engineering intervention, the locomotive was brought in for inspection and the number 8 fuel jumper was found with pitting on the seat and determined to be the source of the leak. The fuel jumper was repaired and the locomotive returned to service.

Based on the findings, the client discussed the presence of a pitted fuel jumper with the engine shop so they can review their component inspection criteria and ensure that all components that are inspected and reused in an engine built are fit for purpose.

Advantages of Oil Analysis identifying Fuel Dilution –

  • 2%-5% Fuel dilution is considered excessive and needs immediate maintenance action
  • Prevent Engine wear particularly in cylinder/ring area cause due to thinning of Oil film
  • Early detection of fuel Dilution through oil analysis is vital in preventing engine failures.
  • Avoid crankcase explosion


locomtive-crankshaft2Ongoing oil analysis provides a mechanism for predictive maintenance which will provide early warning of potential problems and prevent costly engine failure. This incident also emphasises the importance of a timely response to requests for post oil analysis inspections for fuel or metal wear changes within an engine or compressor.

It only takes the saving of one or two engine failures to underwrite the cost of the oil analysis programme.

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