Oil changes: Warm or Cold?

[mcfarmall]

Here's another thought for the lubricologists: Aren't multi viscosity oils designed, for example 5w-30, to have the viscosity of a SAE 5 at LOW temperatures and the viscosity of SAE 30 at HIGH temperatures? That was the whole point of a multi viscosity oil, so you wouldn't have to switch viscosities seasonally...a 5w in the winter and a 30w in the summer. So theoretically, you would want to drain cold, as the oil would behave like a SAE 5 which would flow better and get all the nasties out of the oil pan.

The ideas and thoughts shown above are NOT sarcastic in nature but actual discussion points not meant to invoke feelings of humor.

 

[Looking4new]

I change my oil hot. It is the way that I was taught.

 

[Ford850]

Multi viscosity oils do not get thicker as they warm up. They 'thin' at a slower rate as the oil temperature rises, and thicken slower as the temperature drops. A 5w40 flows like cold 5 weight oil when cold, and flows like hot 40 weight oil when hot. Hot 40W oil flows better than a cold 5W oil, so hot 5W40 flows better than cold 5W40.

 

[Spindifferent]

Politics, religion, oil change interval, synthetic vs conventional, and now warm vs cold. To each their own, I say.

 

[ArlyA]

So a warm engines used oil will flow out quicker when changed and maybe carry more debris out with itself. I'll stick with warm oil changes, politics and religion notwithstanding.

Multi viscosity oils do not get thicker as they warm up. They 'thin' at a slower rate as the oil temperature rises, and thicken slower as the temperature drops. A 5w40 flows like cold 5 weight oil when cold, and flows like hot 40 weight oil when hot. Hot 40W oil flows better than a cold 5W oil, so hot 5W40 flows better than cold 5W40.

 

[CobyRupert]

A warmer engine will simply speed things up. Why not do it (so it) flows out quicker??

because...:
I'm impatient and want to change oil now, even though I haven't used tractor. So this means an unnecessary cold start (the wear and tear of this is not a big deal), but this time of year it means plugging tractor's block heater for an hour or two, and maybe even having to hook up a battery charger for an hour or two (or use boost mode etc...)

Yes, oil FLOWS out quicker, but you've spread it around the engine and hot oil will still take awhile (longer?) to drain down to the oil pan as completely as an un-started engine with cold oil. (When I change hot oil and then dump the oil catch-pan into a pail, there's always some left in the pan. Only when I leave the pan tipped up for a couple days does it completely drain.)

- So hot or cold, I guess how long does one leave the oil plug out is another separate question?

Here's another question to ponder: Does colder (more viscous) oil falling out the drain hole, "pull" more oil with it than warm (less viscous) oil?
(That is, does a more viscous fluid leave less droplets behind?)

 

[CincyFlyer]

"Hot" is the only correct answer. Every piece of equipment I've ever owned says to warm up the engine. Every Japanese auto and motorcycle manufacturer says to do so. Mahindra says to do so. More "stuff" is suspended in the oil, and the thinner oil has a higher "exit velocity". I pull the plug as soon as I stop the engine, then I work on the filter. I clean/replace air filter and other items. I don't put the plug in until there is essentially no more coming out of the sump or oil pan.
Reductio ad absurbum: At 0°F, you'll never get all of the old oil out in a reasonable time. Any stuff that's settled may stay in the pan. Nothing to lose, everything to gain, by changing hot.

 

[deserteagle71]

"Hot" is the only correct answer. Every piece of equipment I've ever owned says to warm up the engine. Every Japanese auto and motorcycle manufacturer says to do so. Mahindra says to do so. More "stuff" is suspended in the oil, and the thinner oil has a higher "exit velocity". I pull the plug as soon as I stop the engine, then I work on the filter. I clean/replace air filter and other items. I don't put the plug in until there is essentially no more coming out of the sump or oil pan.
Reductio ad absurbum: At 0°F, you'll never get all of the old oil out in a reasonable time. Any stuff that's settled may stay in the pan. Nothing to lose, everything to gain, by changing hot.

Thank you!

People seem to forget that there's more than just minute metal particles in that used oil. The oil filter takes care of those. Its the "products of combustion" - the acids, soot, water, etc. (even unburned fuel that's made its way past the rings) that need to be thoroughly dispersed and dissolved in the engine oil before the oil is changed and the only way to do that is by running the engine until it is good and hot.

 

[Oldoak]

The best way is the one that make's you feel best.:confused3:

That would apply to many topics here on TBN.

Politics, religion, oil change interval, synthetic vs conventional, and now warm vs cold. To each their own, I say.

:thumbsup:

 

[CobyRupert]

Thank you!

People seem to forget that there's more than just minute metal particles in that used oil. The oil filter takes care of those. Its the "products of combustion" - the acids, soot, water, etc. (even unburned fuel that's made its way past the rings) that need to be thoroughly dispersed and dissolved in the engine oil before the oil is changed and the only way to do that is by running the engine until it is good and hot.

Good point!
....but where are they before you start the engine? Either on the bottom or floating on the top?