Engine Lubrication And Fuel Economy At Low Ambient Temperatures 885020
A low ambient temperature increases wear and fuel consumption in vehicle engines. The startability of the engine and the start-up of lubrication are highly dependent on the type of engine oil (mineral, semisynthetic, synthetic), whereas fuel consumption depends more on the engine type and driving conditions.
The research work in a special cold chamber equipped with a powerful cooling system has so far involved three gasoline engines and two diesel engines. One gasoline engine was also tested in combination with an all-mechanical transaxle. Tests were carried out within the temperature range of +20…−30 °C using different engine lubricants in order to evaluate both lubrication during the initial start-up and fuel consumption during a test period of 30 minutes. Engines were run under both constant and cyclic load. Effects of auxiliary electrical block and oil sump heaters were also studied.
For the same lubricant viscosity class, the camshaft oiling time was reduced as much as by 50 % by using synthetic oil instead of mineral oil. The startability was also improved with synthetic oil, though the oil type had only a minor effect on cranking speed. Friction was lower but compression work (pressure) higher with synthetic oil compared to mineral oil.
The electric block heater aided considerably the starting of the engine, but flow properties of the engine lubricant are also important when using a block heater, because the heater does not normally warm up the sump oil.
Lowering the test temperature from +20 to −25 °C increased fuel consumption by 4 - 9 % for the diesel engines and by 5 - 22 % for the gasoline engines over the test period of 30 minutes. The oil type had only a minor effect on fuel consumption. However, synthetic oil reduced friction losses in all-mechanical transmission considerably. The use of the block heater was found to be profitable for starting, lubrication and fuel consumption both in the gasoline and diesel engines.