Abstract
Lubrication in two stroke engines (petrol engines in particular) is achieved by either mixing directly the lubricating oil (mostly mineral oils) with the fuel (petrol), or by injecting correct amount of oil into the crankcase thereby combining with the freshly induced charge (air-fuel mixture). In either of the two cases, mist lubrication phenomenon occurs. Mist-Lubrication here implies that, due to the nature of working principle of two stroke petrol engines, part of the lube oil supplied to the engine for lubrication equally partake in the combustion process thereby adding to the emission components. Quite a number of research works revealed that vegetable based oils burn much cleaner than their mineral based counterparts, and hence, suggest the utilization of the bio-based oils as replacements to the conventionally used mineral based oils. However, the tribological performance of the vegetable oils needs to be considered in choosing them as replacements for the conventionally used mineral oils. This is not only important, but critical, as it translates into the engines operating life. It is a known fact that the cost of wear in automobiles, especially the engine components, is worrisome and that is what this work intended to address. This research is aimed at determining the possibility of substituting the conventionally used mineral/petroleum based lubricant (SAE 40) with Jatropha oil (non-edible vegetable based oil) as two stroke petrol engine lube oil by comparing their tribological characteristics. In this work, the tribological characteristics of SAE 40 motor oil and those of Jatropha oil was determined using Anton Paar pin on disc Tribotester. The tribology test results shows about 2.4% reduction in wear rate with Jatropha oil as lubricant, but the coefficient of friction values were found to be almost the same for both the oil samples.

Key words: Jatropha oil, Mist-Lubrication, SAE-40 motor oil, Tribology.