Estimating the total lubricant oil consumption rate in agricultural tractors

Lubrication effectiveness is of paramount importance for the durability of machine components and efficient transmission of power. In addition to reducing the wear and friction of moving parts, lubricants remove potentially damaging heat and impurities and reduce the oxidation and corrosion of components. In agricultural tractors, lubricant oils are used in the engine, transmission, hydraulic system, front and rear axles, steering, and braking systems. This means that a substantial amount of oil must be changed at regular intervals, as recommended by manufacturers. This leads to a significant total oil consumption rate whose estimation is related to accurate accounting of tractor operating costs and to environmental impact analysis (e.g., LCA) of mechanized agricultural operations. The objective of this study was to propose a new general equation to estimate the total hourly lubricant oil consumption rate (HTOC) of agricultural tractors as a function of the rated engine power by extending the definition of lubricant oil consumption rate given by ASABE Standard D497.7. To this end, a linear regression analysis was conducted on a training dataset of 91 tractor models retrieved from OECD Code 2 reports. After validation with a dataset of 164 tractor models, the resulting equation for estimating the total lubricant oil consumption had an R 2 = 0.75 and prediction RMSE of 0.033 kg h -1 . The equation was finally applied to an independent dataset of actual oil lubricant consumption rates obtained from a field survey of 118 agricultural tractors operating in northern Italy. Application of the equation to the field survey data showed an R 2 of 0.89 and RMSE of 0.010 kg h -1 between predicted and actual values. Overall, the considered statistical indicators (r, R 2 , RMSE, PBIAS, and NSE) pointed to a satisfactory prediction capability of the equation.