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You are supposed to change your oil after driving it some for two reasons:
1. Warmer oil flows faster, saving you time.
but mainly,
2. Oil that sits will allow the contaminants to settle into the bottom of the pan, where it's less likely the contaminants will drain. By driving your car beforehand, you get the contaminants to be suspended in the oil and then drain more out.
It's not a huge deal either way though.
Lastly, your oil filter does not drain out overnight....that's fairly stupid and shows an ignorance of our oil filter AND oil filters in general.
First - Our filters are mounted horizontally and the inlet/outlet for oil is in the middle of the filter. So no matter what, it's never going to drain more than 60% of the oil contained therein.
Second - Our filters, and almost all modern filters, have anti-drainback valves. Essentially it's just a valve that prevents the oil from draining from the filter WHEN there is no pressure being exerted by the oil pump (i.e. the car is off).
The purpose of the anti-drainback valve is to ensure that each time the car is cold-started (the hardest time on an engine), that the engine has immediate oil pressure and does not need to re-fill the oil filter every time.
So no, letting your Civic sit there overnight does not allow any additional oil to drain from the filter.
Joe
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