RESEARCH ARTICLE A durability study of a compression ignition engine operating with Thumba (Citrullus colocyntis) vegetable oil Narayan Lal Jain 1 & Shyam Lal Soni 1 & M. P. Poonia 2 & Dilip Sharma 1 & Anmesh K Srivastava 1 & Hardik Jain 3 Received: 1 March 2018 /Accepted: 14 January 2019 # Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract Vegetable oils are found suitable alternate of diesel fuel as per the results of short-run studies. Long-run studies with vegetable oil as a fuel pointed out the problems related to wear and maintenance of the engine. A single cylinder, variable compression ratio diesel engine was tested for 512 h (32 cycles of 16 h per day) to investigate longevity implications of fueling Thumba vegetable oil. Results of the study revealed that a very little damage was observed over the running surface of the cylinder liner, piston rings, valves, and valve seats. Wear in the piston outer diameter was observed to be 13 to 30 microns. Cylinder wear was about 80 microns. The closed gap in the oil piston ring increased up to 200 microns. Heavy carbon deposition was found on different internal parts of the engine, which indicates poor combustion of fuel. Amount of copper (66 mg/kg) and silicon (112 mg/kg) dissolved in the lubricating oil was found more than permissible limits (Cu 50 mg/kg, Si 25 mg/kg), after 450-h engine test run. But all the dissolve materials remain in allowable limits when the durability test conducted with diesel. Smoke, CO, HC, and NO X emissions were found to increase initially then decrease in the further engine running hours. But these emissions were found inferior to the engine emissions fueled with diesel in all the running hours. CO2 emissions were found superior throughout the test with the preheated T20 Thumba oil blend than diesel. The maximum reduction in the viscosity of the lubricating oil, during endurance testing, was found 60 centipoises but it was found 25 centipoises when the test conducted with diesel. Keywords Thumba oil . Wear analysis . Straight vegetable oil . Variable compression ratio . Compression ignition Introduction Diesel engines are widely used in the rural areas of developing countries in different agricultural activities, but the economic considerations of rural areas have restricted their extensive use (Hossain and Davies 2010; Ramning et al. 2013). People of rural areas have low energy consumption due to high price and less availability of energy resources, but they can fulfill their power requirement by generating power on their own using vegetable oils as a fuel in stationary diesel generators and tractors, vehicles, and diesel engines used for agriculture and irrigation purpose (Agrawal and Agrawal 2007; Sureshkumar et al. 2008). Vegetable oils are renewable and greener source of energy. The possibility of different edible and non-edible vegetable oils as fuel for the compression ignition (CI) engine has been accessed but these oils have not been used widely due to their limitations of high viscosity and low volatility. These oils have a comparable energy density, cetane number, heat of vaporization, and stoichiometric air/fuel ratio with mineral diesel (Agrawal and Agrawal 2007; Rakopoulos et al. 2006). Vegetable oil can replace and reduce the Responsible editor: Philippe Garrigues * Narayan Lal Jain narayanjain.c@rediffmail.com Shyam Lal Soni shyamlalsoni@gmail.com M. P. Poonia mppoonia11@gmail.com Dilip Sharma sharmadmnit@gmail.com Anmesh K Srivastava anmesh.k.srivastava@gmail.com Hardik Jain hardikjain465@gmail.com 1 Malaviya National Institute of Technology, Jaipur, India 2 AICTE, Delhi, India 3 Vivekananda Institute of Technology (East), Jaipur, India Environmental Science and Pollution Research https://doi.org/10.1007/s11356-019-04237-8