Draining Oil Hot or Cold?

[John912]

A few years ago I broke with a long tradition and started to drain oil cold not really knowing if it made a difference. An article in Road Racing World, a motorcycle magazine, has an interesting article on the subject. It concludes that while oil flows better when hot, it takes more time to drain back into the sump; particulates smaller than 10 microns not captured by the filter will stay suspended in the oil even when cold; and more water and fuel contaminants will drain out with cold oil (warm oil spreads more of the contaminated oil throughout the engine increasing the amount of contaminated oil left behind and mix with the fresh, clean oil). Something to think about!

[fizeus]

In my knowledge it's better to drain oil when hot.
That's because it flows better and heavy particles are more probably suspended, this is particularly important because heavy particles are more prone to make-up crud and then clog (even partially) piston squirter and oil recesses.
Modern oils contains additive to keep engine clean and those additives need heat to work.
Light particles with hot oil should still be suspended (top or bottom should be not a problem whit an engine containing 10 litres of oil)

If you are worried you can always do a double oil change... I do this sometimes on my engine.
Drain the oil when hot and fill with new oil.
Warm up the engine and let it sits until cold.... Drain again (you can store it for future uses/draining cycles) and fill with new top quality oil.

[sithot]

Warm-hot. Flows better.

[gled49]

When I let contaminated oil stand in a light colored container, the particulates settle to the bottom. I don’t think cold oil will flush and move out the settled particulates like hot oil. I let my oil drain for 4 or 5 hours to let all trapped oil escape.

[The chief]

I drain everything cold. It drains faster and I'm thinking more thoroughly since all of the oil has had time to settle into the crank case. I use full synthetic so no concern about viscosity change due to temperature. I think it's probably not that big a deal to drain hot or cold though. The more important thing in my mind is that the oil gets changed regularly.

[ejboyd5]

How about lukewarm?

[NZVW]

I always did it when HOT but I am clumsy and always used to burn myself so I tried COLD but it took tooo long. I never thought to try LUKEWARM but have now opted to make my son (13yr old) take the plug out when the engine is REALLY HOT.