Oil changes...When engine is hot, warm or cold???

[cnyeco1]

OK. I have been changing my own oil now for 25 years. And when I was always told to change oil after the engine has cooled off for a while. Today a mechanic told me I am doing it all wrong, that I should change it when the engine is cold so that the oil in the engine has settled.

So what do you other mechanics say???

Thanks in advance.

 

[shampoop]

I say hot. More of the old oil and crud it has in solution will come out. The solubility of the contaminants increases with temperature.

 

[sscustom]

hot is prefered when its cold it takes longer to leave the sump, its get sludgy ...

 

[darkk]

I do changes after it has been run a while to get everything warm and off the walls. I let it cool enough to work with the hot parts.

 

[MrMark]

I don't think it really matters. The guy saying cold may have a point but I imagine it drains back down as much as it is going to within 5 minutes. You wait a couple minutes at the gas station to check your oil right? That oil is fully drained down into the crankcase and it is still plenty warm. I would change it when warm to speed up the draining. I think that is the right answer.

 

[Justanoldguy]

I doubt it makes any difference.
What % would be left whether hot or cold?
Not enough to contaminate the new oil anyway.

More importantly is how often you should change it.

 

[ManxRacer]

I vote for hot. Freshly circulated oil will hold contaminants in suspension for a period of time that varies depending upon the nature of the oil. Ironically, traditional oils hold contaminants in suspension better than synthetics. Once the oil is allowed to go static and cool, the contaminants begin settling out into various places in the engine where oil pools.

There are all kinds of opinions out there of which mine is just one, of course. I once knew a guy who swore that you were supposed to check the oil level with the engine running. Another was adamant that engines should always be run to redline before shifting.

If you really want to get one going, ask whether it's better to break in an engine gently or vigorously...

 

[2Big2Ride]

Oil changes...When engine is hot, warm or cold??? Yes.

 

[Rossco]

HOT! The properties of Oil change's when Hot .. Thats what I was told during schooling.

Not sure about motors with Hydraulic Tappets thou . MM

 

[GTVi]

The oil should be warm-hot to the touch, i.e. after idling the engine for 5-10 minutes. When the mechanic says "cold" I presume he means "engine cold" which means not quite operating temperature...its in the context of the engine not the human touch. He may have been misinformed himself and may think otherwise.

Perhaps the other reason is to not shock a "hot" engine with "cold" oil when pouring it in....but this will depend on engine temperature and ambient temperatures in the extreme case.

 

[ludakris04]

I really dont think it matters much. Your only going to get so much out anyways. I prefer to do it cold only because I used to work as a Lube Technician way back when and absolutely hated when someone would come in off the highway and ask for the 30min or less oil change. You could barely touch the oil filter it was so hot.
I also let it drain for a good long time and check everything else out on the car. Its my "me" time.

 

[Rossco]

The oil should be warm-hot to the touch, i.e. after idling the engine for 5-10 minutes. When the mechanic says "cold" I presume he means "engine cold" which means not quite operating temperature...its in the context of the engine not the human touch. He may have been misinformed himself and may think otherwise.

Perhaps the other reason is to not shock a "hot" engine with "cold" oil when pouring it in....but this will depend on engine temperature and ambient temperatures in the extreme case.

Its tricky to define HOT and COLD ..

Hot = Smoking Hot from being ragged around the block?

Cold = Stone cold, Stood overnight?

I would just say hot = operating temp ..

 

[The J]

It's a lot nicer not to have scalding oil draining on you!

I like the oil at a 'warm' temperature. Flows out quickly but you're not burning yourself on the oil pan or oil filter.

If I've been driving, I'll give it 20 mins to cool down while I get the tools out. If it's an oil change after the car's been sitting overnight, I'll let it idle for a minute while I get the car up on ramps.

You're never going to get all of the old oil out so it's a matter of comfort for me.

 

[shoot summ]

I'm in the "don't think it matters" camp.

How is all of this "particulate" getting past the oil filter?

Oil that "pools" in different parts of the motor will pool there whether it is hot or cold, the only oil that comes out is in the drain pan(and filter).

Hot or cold there is always a little oil that remains in the pan.

Regardless mine is typically at operating temp when I take it in to have it changed...

But if I change it I don't purposely heat it up, I just do it when I feel like it, if that is Saturday morning before it has been driven then so be it.

 

[toyotadriver]

I change it with the engine warmed up to operating temps. I think that it flows out better because it's thinner and drains easier.

 

[eldirector]

Guess I'll vote warm. Only because I have to move whatever I'm working on over to my garage first, so it is slightly warm to the touch. I'll also let it drain for a good 30 minutes while I do other stuff.

I hate burning my hands with hot oil!

 

[EYEHAVEYOU]

Engined warmed up to operating temperature so that the oil flows out better, my vote.

I use 10W60 in my car, I can't imagine trying to do it with the car cooled off.

 

[Cobra_Bob]

My opinion is that it does matter. I think you will have the greatest percentage of particulates suspended in the oil if it has been thoroughly agitated. To optimize the oil change, do it after running it at operating temperature. After about 15 minutes to set up (ramps, drain pan, tools, beer, etc), go for it. Let it drain for at least 30 min (dirtiest oil comes out last). Elevate other corners of vehicle to ensure thorough drain.

 

[Crizzle]

I was taught as a kid that "the last drop is always the dirtiest." I always get the car up to operating temp before changing the oil.

 

[jeepjunky]

Ive always been told hot. If the oil is hot, the engine has been running and any "gunk" will be well mixed with the old oil. thus more gunk leaves the engine when drained

 

[Shadowdog500]

I do mine hot. If you are that concerned you can leave the pan under it for a day that way it will be drained both hot and cold.

If you are super concerned, someone here indicated in a recent thread that he changes his oil and filter then runs it for a few miles and changes both again. He said he would do this several times until the oil came out clean. Way overkill for me.

Chris

 

[DoyleDee]

I like to drop the pan when I do an oil change.....

Lol, j/k... You're not going to get all the oil out anyway....unless you could flip your car over and over to get it to flow to the pan. I think it matters more that you change it in a timely manner..depending on how many miles and conditions you drive in. I generally do it warm, but don't really think that matters..big particulate will settle anyway.

 

[rockchucker]

After it has been run to normal operating temperature, let sit for a few minutes. While I am getting the car up in the air I will place the jugs of Oil on the top of the Engine so they warm up also. This will take care of the "Shocking" someone mentioned when pouring in the new Oil. Pull the Plug and the Filter and let it drain for as long as I am working on it. Fill the Filter up with Oil if possible, Plug with a new Washer and fill it up. Fire it up and let it Idle for 2-3 minutes NEVER revving the Engine. Shut it down and top it off after a few minutes of letting the Oil drain back into the Oil Pan.

 

[Kev442]

Warm camp. I wait 45-60 minutes after parking hot. I hate burning my hand on 250 degree hot oil.

 

[Tscott]

I change mine while the engine is running, that way I make sure to get all of it out of the engine.

 

[NeilH]

i vote for smokin HOT.

 

[tig]

Hot. As others have indicated: it flows better and freshly circulated oil will hold more contaminants. Like ManxRacer says:

I vote for hot. Freshly circulated oil will hold contaminants in suspension for a period of time that varies depending upon the nature of the oil. Ironically, traditional oils hold contaminants in suspension better than synthetics. Once the oil is allowed to go static and cool, the contaminants begin settling out into various places in the engine where oil pools.

I once knew a guy who swore that you were supposed to check the oil level with the engine running.

You ARE supposed to do this with air cooled Porsche engines. Really.

If you really want to get one going, ask whether it's better to break in an engine gently or vigorously...

Oh, gawd, don't start that one!

 

[Shadowdog500]

I change mine while the engine is running, that way I make sure to get all of it out of the engine.

This is why I do all of my own work!

I know you are joking BUT I know a marine mechanic who does it that way. The oil drain plugs are a pain to get to so he literally disconnects the oil pressure sender and hooks a hose to the threaded hole. Then he starts the engine and shuts it off when oil stops coming out of the sender hole.

When I worked in a shop we had an idiot on the evening shift who would sometimes "make the engine work for it's oil" after he drained the oil he would start the engine before pumping the oil in one quart at a time.

Chris

 

[bentwrench54]

When I worked in a shop we had an idiot on the evening shift who would sometimes "make the engine work for it's oil" after he drained the oil he would start the engine before pumping the oil in one quart at a time.

Chris

that's too funny!

oh, and i prefer my vehicle's oil as warm as i can stand it when i change oil, whether at home or at work.

in the winter time i can set a cold hand up near the oil pan to get warmed up!

 

[PassnThru]

Whatever temp the engine is at when I am ready to change it. If I am ready first thing in the morning then stone cold after sitting all night. If I've been out in the vehicle then I'll let it sit for 30 minutes or so. I will not start it and run it to warm it up to change the oil. It may come out slower when its cold - but it will come out.

 

[v8garage]

Hot!
V/8

 

[justanengineer]

I doubt it makes any difference.
What % would be left whether hot or cold?
Not enough to contaminate the new oil anyway.

More importantly is how often you should change it.

Believe it or not, it does make a pretty significant difference. Been there, graphed the data, dont want to go there again.

As stated preivously, the viscosity changes with temperature and all of the pollutants begin settling out as soon as the engine is stopped. It will flow best when hot and should be drained immediately after running. No, you wont get all of the oil out, but the majority of the **** is where the majority of the oil is, in the pan.

 

[Buford T. Justice]

I always run mine 5 min or so. Oil comes out faster and I believe more hunk comes with it.

 

[4BT]

putting waaay too much though into such a simple procedure. I change my oil hot and cold.....doesn't really make a difference but I do prefer to keep my hands un-burnt

 

[PsRumors]

When it is time to change the oil I always plan it for a trip to town. When I get back the engine is always up to full operating temp. I pull in, onto the ramps, shut it off, open the fumoto valve, poke a hole in the filter and walk away.

No worries of hot oil running down my arm or dealing with a hot drain plug.

 

[NUTTSGT]

Change the oil at whatever tempature you want, I'll do the same.

I change mine when the engine is cold, first thing in the morning after it's settled in the pan.

It seems to me, all the **** that is in the oil, would be settled in the bottom of the pan. Why would you want to circulate that stuff back up through the engine if that's the purpose of changing the oil ?

To each his own, just change your oil.

 

[oldgoat]

I always change it when it is either hot or warmed up. The idea is that anything is then suspended in the oil. Changing it when cold I would think let the gunk settle to the bottom and less chance of it draining out. Probably doesn't matter, but that was the way I was taught and it kind of made sense so I've gone with it now.

 

[Bobby.T]

My brother-in-law had two engine failures in his Dodge pickup, before I learned his oil change routine was to flush the engine with gasoline before adding the fresh oil, to "make sure everything was cleaned out". I no longer discuss any mechanical topics with him--he is beyond help.

 

[Original Man]

My brother-in-law had two engine failures in his Dodge pickup, before I learned his oil change routine was to flush the engine with gasoline before adding the fresh oil, to "make sure everything was cleaned out". I no longer discuss any mechanical topics with him--he is beyond help.

Since you somewhat brought it up, Ive heard a few people say they run ATF through the system briefly to help flush it out. Then drain it and put in engine oil.

 

[NeilH]

Since you somewhat brought it up, Ive heard a few people say they run ATF through the system briefly to help flush it out. Then drain it and put in engine oil.

there is a lot of that going round.

some say run it on ATF to flush it.

some say pour a half pint of diesel into engine and run it before oil change.

sime say the world is flat....


i say give it regular oil changes and disregard any type of engine flush.