Study of Automotive Gear Lubrication at Low Temperatures 920021
Properties of various gear lubricants were studied in the temperature range of +20 - -40 °C. The tests were carried out in the cold research facilities of the Laboratory of Fuel and Process Technology of the Technical Research Centre of Finland (VTT) using the gearbox of a rear wheel drive delivery van as the test equipment. The tests focused solely on the gear and its lubrication. The output shaft of the gearbox was connected directly to the engine dynamometer and the input shaft was rotated by a hydraulic motor.
The aim of the tests was to study the properties of different lubricants in the gearbox at cold-start and start. The most significant reading monitored was the power loss in the gearbox as a function of time. This affects the fuel consumption of the vehicle. The warming-up of the lubricant was also measured, as well as possible changes in the viscosity over the test.
The efficiency of the gearbox increased in five minutes close to the final value of the 40 min test. The power loss (efficiency) at the start-up can be affected by the choice of the lubricant, although lubricants cannot be classified solely by the viscosity class under the coldest conditions. In these tests, in which the load was equal to that of drive at a constant speed of about 80 km/h, the power demand was increased by a poorly flowing lubricant not more than by 5 - 6 % during the first five minutes.
The test temperature had a fairly great effect on the stabilized power loss in the gearbox. For example, the difference between the power losses at the temperatures of -26 °C and +20 °C was on average 0.8 kW, about 5 %.