Effect of Scheduled Inspection and Preventive Maintenance on Exhaust Emissions and Fuel Economy

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The level of emissions and fuel economy at the maintenance stage of an automobile was studied on the DAF TB 2175 PE and YAXING JS 6120 GIH buses at the workshop of Metro Mass Transport Limited in Kumasi – Ashanti Region. The opacities of exhaust gases from the buses were measured with the OPUS 50 gas analyzer before and after servicing the buses. The buses were made to travel a total distance of 5000 km after which emission levels and fuel economy (distance travelled when 1 litre of fuel is consumed) were measured. Results indicated that emission levels reduced from 7.94% to 2.32% (a drop of 70.78%) for the DAF TB 2175 PE buses and from 5.27% to 3.20% (a drop of 58%) for the YAXING JS 6120 GIH buses over the study distance. These indicate that maintenance has great tendency to reduce emission levels, barring other factors such as driving pattern, fuel quality and traffic situation. Also the study revealed that after servicing the DAF TB 2175 PE buses could cover a distance of 2.775 km per litre of fuel instead of a shorter distance of 2.576 km with the same amount of fuel after 5,000 km (a drop of 7.2%). A similar observation was made for the YAXING JS 6120 GIH buses which covered 2.76 km after servicing and 2.55 km after 5,000 km, using one litre of fuel in each case. Additional 140 and 149 litres of diesel are needed to travel a distance of 5000 km by the DAF and YAXING buses respectively if preventive maintenance is ignored. These are at respective costs of GH¢241.36 and GH¢256.88 for the DAF TB 2175 PE and YAXING JS 6120 GIH buses, given the current price of diesel as GH¢ 1.724 per litre. Although other factors such as fuel quality could influence engine performance, the results suggest statistically significant improvement in exhaust emission reduction and fuel economy, calling for vehicle operators including governmental and non-governmental organizations to be well resourced and encouraged to undertake scheduled maintenance to save resources and reduce pollution.
A thesis submitted to the Department of Materials Engineering of the College of Engineering, in partial fulfillment of the requirement for the degree of Master of Science, in Environmental Resources Management, February-2011