[cas951]

my preference is to warm up (Not Hot) the car to circulate the oil in the system and let it cool a little before draining the oil. The reason for this is you want some oil in the journals before starting the engine after the oil change. Keep in mind the oil filter housing is empty when you change the oil and new oil will take a little time to reach the journals. This is a safety precaution. I normally allow the oil to drain about an hour to try to drain as much as possible.

The engine should be cool when changing the plugs. This is for your own safety as well as the engine when removing hot components.