Lubricating oil in a motorcycle engine gets pressurised by a pump and goes to an oil gallery, from where it splits into two paths: one to the cylinder head and the other to the crankshaft, via the cover clutch. Oil to the cylinder head travels through the entire length of the oil gallery in the crankcase, and then through a small hole at the top of the crankcase (around 2 mm) it fills up and goes to the annular space between the cylinder stud, rises upwards and lubricates the valvetrain and stuff. Now, there is a thing called "EFFECT OF FLOW TURBULENCE ON TEMPERATURE" right? My doubts are: 1) How does the length of the oil gallery affect its temperature? My own reasoning goes like this: the longer the length of the oil gallery, the more the friction loss and the more the oil gets heated up. Also, the oil gallery is bent. What happens to the temperature of the oil in the bend? Does it increase, or does it decrease with the bend radius? The more the bend, the higher the temperature the oil gets heated up to, right? Or wrong? 2) Even if temperature increases with the length of the oil gallery, does not all that heat get dissipated via the conductive surfaces (the walls of the oil gallery)? Ultimately does not the temperature decrease? 3) How does a sharp bend (around 120 degrees) affect the fluid temperature? Does it increase or decrease? 4) What is the effect of flow turbulence and bend turbulence on the oil temperature? Is it in any way related to the 3 questions I have asked above? I'm confused as hell. Please tell me the effect of bends and sharp edges in an oil gallery on the oil temperature. Thanks a lot in advance.