thunder911

Greetings,

Hope are of you are doing well.

I usually take a quick drive 20-30 mins then let the car cool down before I let the drain plug loose with warn (not not) oil.
But, now I have a quick question on doing it with cold oil because I haven't had a chance to drive my car for a month+ now.
I read and heard that some people always do a change with cold sitting oil vs. warm or hot oil because having the car sit for a while will let most of the oil drain to the bottom than running the engine/cooling it down. It makes sense that most of the oil in the engine would fall to the bottom due to gravity.

Also, since our oil is 0w40, the velocity issue really doesn't make a diff by running the engine/cooling it down vs doing it cold.

Any takers on comments?

Thanks.

anewman

Cold is fine, it's just going to flow more slowly so plan on it taking longer to drain. Don't over think it.

dgjks6

Measure how much comes out. I get more out when it's cold

jchapura

Regarding cold drain, if there are suspended materials in the sump, won't more of them be settled and not drain out (because they are left in the film on the sump plate upper side)? Conversely, warm drain suggests that the engine was recently running and keeping these materials in suspension (due to mixing) to allow for better overall removal of them.

And also, since the cold oil is thicker won't that leave more of the suspended materials in the sump for a typical, normal drain time? How much cold draining extra drain time is needed to have equivalent draining (to warm/hot draining)?

linderpat

^^^This. Always do an oil change with a warm engine. You want to make sure the particulate matter is in suspension, and drained out as much as you can. Drain warm, and let sit for a long time to allow everything to drain out. Remove oil cap and filter to allow max draining as well.

Petza914

You should.release the plug as soon as you get back from the drive so any junk is suspended in the oil, then let it drain for an hour before putting the plug back in. Just do other maintence stuff while you're waiting.

Cold 0 or 5 viscosity rated oil is still thicker than the hot 40 viscosity rating. The two aren't interrelated since those indices are at different temperatures.

Fullyield

You must change oil while hot (after driving car to oil operating temp) IF you are sending a sample for used oil analysis to Blackstone or Speed Diagnostix to get accurate results. If concerned about removing all the oil, let car drain overnight as many on here do.

Bruce In Philly

2009 C2S 177K miles

I think I am the one you are referring to who does cold oil changes... yay!

First and foremost, no own has demonstrated that cold oil changes (from a sitting car not started) results in particulates gathering flat on the sump pan and further, don't drain out with the oil flow. While at first thought, it makes sense.... I kept spent oil on the shelf for months and never saw the bottom of the bottle be darker than the top. My reasoning (no real science here either) is that any particulate that would fall out of suspension in a week or so of sitting would be of a size that the filter would catch (remember that filter?). Again, no science here. And lastly, I do 5K oil changes... I mean really, with this over-maintenance, I just don't believe I am damaging my engine by changing cold oil in a car that hasn't been started or moved in 3-7 days. On top of all this, I jack up and down each side of my car high to drain even oil trapped in the various places up there and do get out more oil than what I think even a dealer change would get (assuming dealers are the gold-standard of oil changing).

What I love about oil change threads is that so few of us posters have any real science... just reasoning based on assumptions. That is OK, that is part of the entertainment here and I sure am entertained by all of us but mostly my own neurosis.

Peace
Bruce in Philly (now Atlanta)

ManoTexas

Change mine cold.

PV997

Gotta agree with you Bruce but I'd add that reasoning based on assumptions would be fine if those assumptions were backed by hard evidence. Most of the time they aren't, they are folk tales more akin to superstition.

Is it better to drain the oil hot? Yeah, maybe at some theoretical infinitesimal level. Does it make any difference in the real world? Unlikely, particularly if one is doing regular oil changes. Just like waiting an hour to drain the oil to get those last ounce (out of 88 ounces total) makes no difference in the big scheme of things. If you DIY and mow the lawn while it's draining that's great. If you are paying $150/hour for some guy to watch your oil drain that superstition can be costly. Makes you wonder how many of these folk tales are started by people who profit from them.

Do whatever works and don't worry about it. Save your worry for that new covid variant that's going to kill us all.

jchapura

That's the thing, we don't (personally) know what works (best) so we come here to try to discern it from others' experience (and hopefully data).
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And even better when we can learn that "best" can be practiced for essentially no more cost than "good enough".

Unfortunately, IMSB and bore scoring have made us a bit gun shy ($30K engine v. 2 extra drain time hours per year, for example? - no brainer) and that drives us to find the best practices for maintenance and schedules.

Newt Gomez

Not sure why it's up to debate, but draining warm is always best due to suspension. If you've ever peeped at any tractor service manual, they ALWAYS tell you to drain warm. Given, these aren't diesel engines, but dirty oil is dirty oil.

Floyd540

Choose your method warm or cold and be happy. As Wayne says you are only getting some of the oil out, not all of it like an ole timey splash and hope system with an oil pan for a sump. The "wisdom" about only doing it warm dates back almost a hundred + years ago when oil filters were not used. Even by 1940+ oil filters were optional and then they were not full flow anyway. They were partial flow where only 5 to 10% went thru the filter per pass. All modern cars have full flow filters so the problem is not a problem. That coupled with the additives in modern oil help carry away any suspended crap and leave it for the filter. Old timey oil had no additives and moisture and carbon and blowby created a mess that settled into the oil pan making a mucky mess. If you have ever had an engine apart from the old days, you know what that is. So if you learned your car stuff from an olde timer, then you were schooled to do it warm-period. The oil was really terrible in the old days- old days being 40 to 150 years ago.
Change your oil- and filter and be happy!

ManoTexas

PV997, I let mine drain till almost none coming out for one reason. Minimize oil on gloved hand when installing new plug. Not for any technical reason. I’m just clean up lazy. Or as my wife says, just lazy.

140.6er

I’m a warm/hot oil drain guy but only because my grandfather was a mechanic on PT boats in the Mediterranean during WW2. He wagged his finger at me and warned me of the horrors of cold drains. He taught me much about engines and engine care but it certainly was outdated. At the end of his storied life, he relented and marveled at the improvements that followed from full flow filters and modern oils. To be honest, I do the warm, really hot, changes as homage to him even though I know it doesn’t matter in the long run. I drain and change every 5000. By the way, I’m still trying to perfect the mess free plug removal method.