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The quote in #2 above answers one of your questions.
There is no clearance for any lubrication.
"...the piston expands faster than the cylinder and the clearance becomes too tight, which makes it impossible to gain boundary layer lubrication..."
Which is why the advice is - 'don't start the engine in very cold weather'.
In marginally cold situations, lighter oil may make just enough difference to avoid scoring but I have read no precise definitions of the parameters.
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2001 Boxster S
Engineers muse
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