Using an automobile gasoline engine (73 mm bore × 71 mm stroke), temperatures of crankpin bearing and other related parts were measured by thermocouples. The thermocouple wires were led out from the crankpin bearing through the connecting rod, the pistonpin, the piston, the combustion chamber and the cylinder head. A better understanding of the behavior of crankpin bearings has resulted.Presented as an American Society of Lubrication Engineers paper at the Lubrication Conference held in Minneapolis, Minnesota, October 18–20, 1966.