Originally Posted By: flash_os
Is 5w-20 has better adhesive to metal than 0w-20 in cold weather?
Since 0w-20 has lower thickness on cold weather thus less adhesive when you left your car for a night more oil will be in oil pan.
Somebody tried to test it on any car scrap metal in your garage environment?
Oil never fully drains down, not even the thinnest synthethic 0W-20 or 0W-16, there is always a film of oil left, that is enough to lubricate the engine for the first few seconds of running until the oil has flowed everywhere.
The one and only time in an engine's life that there is a true "dry" start would be the first time the engine is ever run after being put together, or after a rebuild, although every engine rebuilder i know uses plenty of oil and grease on bearings and such when putting together an engine, and they prime it up first before starting it.
Some oils have greater polarity, meaning they wll "cling" a little more to metal than others after shut off.
Conventional oils, specially something thick like a Group I 20W-50 loaded with sticky VII's "sticks" more to metal than say a Group IV PAO synthetic, they drain off faster.