Effect of Biodiesel Utilization on Tribological Properties of Lubricating Oil in a Compression Ignition Engine - Novel Combustion Concepts for Sustainable Energy Development - page 79

observed lower wear for B20-fueled engine. Pb and Al were found slightly higher
for B20-fueled engine, which may be due to the attack of biodiesel on paints and
bearings (Sinha and Agarwal 2010 ). Agarwal et al. ( 2003b ) demonstrated that wear
metals

debris such as Fe, Cu, Al, Pb reduced with increasing biodiesel of palm oil
into blends, which produced the lower level of wear concentration than that of
mineral diesel, and the reason is the effect of the corrosion inhibitor in fuel and
lubricating oil which controls corrosion as well as oxidation of the lubricating oil.

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4.4 Viscosity

During engine operation at normal temperature, a minor quantity of fuel normally
dilutes the lubricating oil, which escapes to the oil sump along with blow-by gases.
Engine cold-starting, rich fuel air mixtures, and low ambient temperatures promote

fuel dilution of lubricating oil. Also dilution of engine oil occurs when the fuel is
injected late in the combustion cycle, in order to regenerate the diesel particulate

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filter, typically used for trapping particulate emissions in modern engines (Uy et al.
2011 ). Fuel dilution reduces lubricating oil viscosity and the concentration of
engine oil additives, potentially compromising lubricant

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s performance. Inadequate
oil viscosity affects oil film formation and load-bearing capacity, which can
potentially lead to excessive wear of bearings, journals, and other moving com-
ponents, in addition to low oil pressure and poor oil economy. There are two main
factors responsible for the viscosity changes affecting the oil in opposite direction.
Formation of resinous products because of oil oxidation, evaporation of lighter
fractions, depletion of anti-wear additives, and contamination by insolubles tend to
increase the viscosity, while fuel dilution and shearing of viscosity index improvers
tend to bring down the viscosity. Biodiesel usage may compound these issues due
to its oxidative instability and its higher boiling point compared to mineral diesel,
which increases its concentrate in the oil sump.
During the durability test of the engine for biodiesel, viscosity of lube oil
samples was evaluated at 40 and 100

C using kinematic viscometer (Agarwal
2003 ). The extent of lowering of viscosity of the lubricating oil was lesser in case of
biodiesel-fueled engine compared to diesel-fueled engine. This may be because of
lower fuel dilution. Fuel dilution is a direct consequence of clearance between
piston rings and cylinder liner (Agarwal 2003 ).

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4.5 Ash Content

In order to find the ash content, lubricating oil samples need to be kept in the

furnace at 450 C for 2 h to produce ash. The residual ash

contains metallic wear debris. Ash content in the lubricating oils for biodiesel- and

° C for 4 h and then 650 °