Design and Fabrication of a Low-Cost Diesel Engine Oil Filtration and Recycling Unit for Roadside Mechanics in Oyo State

Used engine oil disposal by roadside mechanics across Nigerian urban centres constitutes a persistent environmental hazard, as unregulated discharge of waste oil into drains and soil contributes to groundwater contamination and public health risks. This study presents the design and fabrication of a low-cost used engine oil filtration and recycling unit intended for small-scale automotive mechanics in Oyo State. The unit employs a two-stage filtration system comprising a coarse particulate filter, a fine activated clay filter bed, and a mild heat treatment chamber for viscosity restoration and moisture removal, assembled within a portable welded steel casing. Design parameters including filter media sizing, flow rates, and heating element specifications were determined based on the rheological requirements of re-refined engine oil for secondary applications such as chain lubrication, mould release, and industrial rust prevention. Performance tests were conducted using waste oil samples collected from ten mechanics in Ibadan, and filtered oil viscosity, contaminant removal efficiency, and water content were measured before and after processing. The filtration unit removed 94 percent of solid contaminants and reduced water content to below 0.5 percent by volume. Processed oil viscosity fell within the range suitable for secondary lubrication applications. Total fabrication cost was 57,000 naira. Keywords: engine oil recycling, waste oil filtration, environmental protection, roadside mechanics, Oyo State.