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Originally Posted by Lucky
...The term "pre-lube" usually refers to a system that builds oil pressure before you turn the ignition key to start the engine. This is common practice on race cars since their engines are often built to very tight tolerances and are usually filled with a thick oil which offers maximum protection at high loads, so significant wear would occur at start up before oil would circulate and build pressure...
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Actually, that's not entirely true. Race engines are built to varying tolerances, some of which are actually quite loose. This reduces friction and drag and allows for higher revving and cooler running. They are however built to
exact tolerances, but not necessarily tight ones.
Valvetrains are typically built to pretty close tolerances while bearings, piston rings and wrist pins have fairly loose tolerances.
The loose tolerances are only part of the reason heavier oils are used, but also heavier oil is more massive/unit volume and so can carry away more heat. Heavier oils are also more stable at higher race temperatures.
