| Summary: | Engine oil plays an important role in reducing the friction and wear between the metal parts of an
engine and acts as a coolant to lower the engine temperature. Mineral oil has been dominated the
market as the base oil for engine oil due to its availability, and good performance. However, due
to the decomposition issues and emission of toxic gases during its use, it becomes a source of
pollution to the environment. The present study aimed at evaluating the alternative base oil for
engine oil which is more environmentally friendly and effective in reducing wear and friction. This
is achieved by blending the mineral oil with biodegradable base oils namely palm oil and
trimethylolpropane (TMP) ester. The effect of adding nanomaterials on the friction properties were
evaluated. The study also investigated the thermal degradation characteristics of the formulated
engine oil in air and inert nitrogen.
The study was divided into three steps. In the first step, TMP ester was added to the palm oil at
the percentages 2, 4, 5, 6, and 7 wt% to obtain the best wear and friction results. TMP ester can
be used as an additive to improve the thermal and oxidative stability of palm oil. In the second
step, the best formulation of the first step was added to the mineral oil at 10, 30 and 50% weight
percentages. In the third step, the nanoparticles were added at 0.25, 0.5, and 0.75 wt% to the best
formulation of the second step to improve the oil performance and reduce the coefficient of
friction (COF) and wear scar diameter (WSD). The results showed that the blend of palm oil
with 2 wt% TMP ester was the best formulation with the value of coefficient of friction at
0.0751 and 485 μm for WSD. Mixing this blend with 70 wt% mineral oil improved the
results of COF from 0.1 to 0.0609 and WSD 565.2 µm to 318.9 μm. To further improve the
performance of the newly formulated engine oil, five types of nanomaterials, copper oxide (CuO),
aluminum oxide (AL2O3), Titanium silicon oxide (TiSiO4), graphene and borosilicate nanoglass
powder were added to the blend. The addition of 0.5 wt% of nanoglass powder reduced COF and WSD further to 0.0565 and 295.5 µm respectively. Adding other nanomaterials yielded
detrimental effects on the formulation, both COF and WSD increased significantly.
This may be due to the additional friction attributed by the nanomaterials.
It was revealed that blending mineral oil with palm oil, TMP ester and nanomaterials improved all
physicochemical properties, such as density, viscosity, viscosity index, TAN and pour point.
It has also been proven that adding palm oil and TMP ester into the mineral oil improved the
thermal stability which exceeded the thermal stability of the commercial lubricants. This is
evidenced from the degradation profiles of newly formulated engine in air and nitrogen
environment. The onset temperature improved from 334.7 ᵒC to 409.6ᵒC. It is also worth-noting
that the blend of palm oil-TMP ester with mineral oil without nanoglass showed better performance
than the oil blended with
nanoglass powder.
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