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Purpose. Lubrication is inevitable for all interacting surfaces in IC engines to avoid
component failure and reduce frictional losses specifically operating under boundary lubrication
regime. Environmental concerns, decreasing mineral oil reserves and difficult disposal of
nonbiodegradable conventional lubricants have urged the researchers to shift towards
environmental-friendly lubricants. In this article compatibility of various ionic liquids with
different bio-lubricants and conventional lubricants regarding their tribological performance has
been studied and compared. Methodology. In this study two potassium based ionic liquids
including Bis(2-ethylhexyl) phosphate and Trihexyltetradecylphosphonium bis(2,4,4-
trimethylpentyl) phosphinate have been checked for their compatibility towards bio-lubricants
including Cotton seed oil, Waste cooking oil, Rattan Jot oil and polyalphaolefin (PAO) etc. The
physicochemical properties including viscosity, density, viscosity index, kinematic viscosity,
flash point, pour point, total acid number (TAN) and total base number (TBN) of bare oils and
their blends with ionic liquids were investigated using different ASTM standards Findings.
Trihexyltetradecylphosphonium bis(2,4,4 trimethylpentyl) phosphinate were completely soluble
in the base oils and are assumed to exhibit better tribological performance. Value. Ionic liquids
are excellent solvents and are easily miscible in bio-lubricants and therefore can be used as
additive with minor modifications. They produce less ash content and hence are environment
friendly. IL-based bio-lubricants have the tendency to replace conventional lubricants regarding
their tribological applications. However, further work on improving bio-lubricant’s wear
characteristics is needed for complete replacement of mineral oil-based lubricants