Quote:
Originally Posted by raleedy
Large quantity of a fluid that has relatively high thermal inertia. But it doesn't need to be really hot like the coolant. 160º F is plenty (the internal temp of well-done beef).
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I'm not sure I'd consider 160F to be "plenty". 160F for oil temperature is the typical "stay under 3000 rpm" point you will see people quote for a turbo engine, and "don't lean on it until over 200F" is another.
There's a reason for this. Take a crankshaft. Assume a nominal length of 18" and assume it's constructed of steel. A typical steel will have a thermal expansion coefficient of .0000073 in/(in degF). Say I had rolled out of my house this morning at 7:30am (24F) and fired my car up. The normal engine operating temperature is 240F. The crankshaft will grow (0.0000073*216*18 inches) = 0.028" in length. Everything fit into a bearing will grow along with the crankshaft, and all of them will increased in diameter. The bearings will grow radially, tightening the internal and external channels.
Where is it at 160F? Barely over half of that growth. Everything is still working to get fit together. You don't want to hit the engine hard at that point, because the critical bearings and shafts (think oil-cooled turbochargers at 6-digit rpm) aren't close to fully seated yet.