This paper presents experimental results carried out to evaluate wear and lubrication characteristics of a multi cylinder diesel engine when operated on vegetable oil blended fuels. The blended fuels consist of 10%, 20%, 30%, 40% and 50% coconut oil (COIL) (in volume basis) with diesel fuel (DF2). Pure DF2 was used for comparison purposes. The engine was operated at constant speed of 2000 rpm with 50% throttle load for a period of 100 hours for each test fuel. The engine was operated for a total period of 600 hours for six fuels. The same lubricating oil equivalent to SAE 40 was used for all the fuels system. The sample of lube oil was collected through a one way valve connected to the crankcase sump at 50 hour intervals. The first sample was collected immediately after the engine had warmed up. The effect of blended fuel on engine component wear and lubrication characteristics in terms of viscosity, total base number (TBN), moisture content, oxidation, wear metals, contaminant elements and lubricant additive depletions were analyzed. The results showed that wear metals, contaminant elements increase with increasing COIL with DF2. An increasing COIL in blends reduces additive elements; and the reduction rate during blends of up to 30% COIL is quite similar to DF2. Soot and sulfation reduce with increasing COIL in blended fuels due to reducing aromatics and sulfur in comparison to DF2. The water concentration increases from above 30% COIL blended fuels. The TBN and viscosity changes are found almost normal. The engine did not have any starting and combustion noise problems when operating on COIL blended fuels. These lubricating oil analysis data will help to select tribological components and compatible lubricating oil for coconut oil or biofuel operated diesel engines.

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