Draining oil - cold vs warm
Discussion
I was taught that you get an engine warm before draining the oil, the theory being that the warm oil will have lower viscosity and will run out more readily.
I was pondering the other day if this actually achieves anything - surely on the cold engine, more oil is sat in the sump than with a hot engine, as it will have drained out of the top end of the engine*? And it's not like engine oil becomes a solid mass at typical UK temperatures, so it's still going to run out of the drain hole (albeit a little slower - however you save the time of running the engine up to temperature if you aren't at liberty to plan your oil changes to coincide with returning home from somewhere).
So, have I been doing a pointless thing all these years, or are there other benefits to warming the engine up before draining down?
*even with NRVs, a head eventually drains out although it takes longer. I find an engine sat for 2 months will have a noisy head on start-up.
I was pondering the other day if this actually achieves anything - surely on the cold engine, more oil is sat in the sump than with a hot engine, as it will have drained out of the top end of the engine*? And it's not like engine oil becomes a solid mass at typical UK temperatures, so it's still going to run out of the drain hole (albeit a little slower - however you save the time of running the engine up to temperature if you aren't at liberty to plan your oil changes to coincide with returning home from somewhere).
So, have I been doing a pointless thing all these years, or are there other benefits to warming the engine up before draining down?
*even with NRVs, a head eventually drains out although it takes longer. I find an engine sat for 2 months will have a noisy head on start-up.
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