Any benefit to changing oil when engine is warm???

[tpattgeek]

A lot of OC procedures say to let the engine warm completely up before change the oil, but is that really necessary? Does it matter if you're using syn vs. dino? Most of the time, I either move my car into place at the house or it's already in place for the change, so the engine is pretty much cold when changing. Is there a benefit to driving around the block first? Wouldn't that just get more oil pumping toward the top of the engine, therefore less in the sump to be drained out? Please excuse my ignorance.

 

[crazyoildude]

change the oil when engine is warm because it will drain out all the bad stuff better.
we have that in the instructions that come with our rebuilt engines

 

[HTSS_TR]

If the car didn't run for several hours the debris, if any, is settled at the bottom of the oil pan and it may stay there when you remove the plug to change oil.

If you change oil right after a good drive then debris is flowing out with the warm oil. To get the most used oil drained out of the engine let it drains for 15-20 minutes.

 

[earlyre]

the above reasons, Plus the implied, but un-stated, warm oil flows better/easier.

(simplified example: fill 2 small containers with cooking oil, place one in fridge for a few hours. then try and pour back into original container)

 

[The Critic]

Considering that most people only allow the old oil to drain for a few minutes, if the oil is warm, more of it will drain out I guess.

Also, all of the factory service manuals I have seen direct the owner to only perform an oil change when the engine is at normal operating temperature.

 

[Artem]

Driving around the block in a cold engine won't do you much good. The engine has to be HOT, meaning a good 15-20 mins of driving.

When an engine is running and then you turn it off, the oil literally takes a minute to drain back into the pan.

It then takes 10-15 mins for the leftovers that are splattered all over the engine to drain down the sides and into the pan as well. (this amount is very small and won't make a difference)

By the time you jack it up, get ready for the OC, crack the drain bolt, remove the oil filter, ALL the oil that can make it into the pan will already be there or in the drain pan.

The main reason to get the oil HOT and give it plenty of time to circulate in the engine is to get all the heavy stuff that's on the bottom of the pan suspended in the oil and then allow it all to drain out quickly.

Every time the engine sits for 8 hours + all the heavy suspended particles in the oil sink to the bottom of the pan. If you drain the oil when it's cold, a lot of the heavy stuff on the bottom of the pan won't get removed with the flow of oil. It will remain on the bottom of the pan and get mixed with the new oil and that ain't good.

A REAL BITOG-er does things properly and changes the oil when the engine is hot

I usually give it 20-30 mins with the hood open to cool off after a long drive before i start working on it. 90% of the time though, i jump right in there while it's all still boiling.

 

[Artem]

Originally Posted By: The Critic
Considering that most people only allow the old oil to drain for a few minutes, if the oil is warm, more of it will drain out I guess.

Also, all of the factory service manuals I have seen direct the owner to only perform an oil change when the engine is at normal operating temperature.


I give it a few mins until the flow stops and becomes a slow drip. waiting another 10-15 mins after that won't remove much. I've tested this by catching the drops in a clear plastic cup. 10 mins later, there's barely enough oil to cover the whole bottom of the cup.

those 30-40 drops aren't worth my time, to be honest with you, esp if the client is standing there waiting for me to finish.

I usually like to finish the OC as quickly as possible, refill and start the engine back up.

The few times that i left the car for an hour or two to drain, during start up, the oil light takes 3x longer to go off and engine noise is MUCH worse, vs quickly starting it back up to get oil pressure where it needs to be.

 

[user52165]

No one, again, no one, is going to augue the alternative.

 

[ltslimjim]

^I had to let me car drain for like 2 hours this summer when my old drain plug failed during the oil change, couldn't reinstall it with bad threads. It turns out now, even the replacement has beginnings of damaged threads so I think it's a problem in the oil pan's threads. Still, I've heard about some oil pumps losing prime if drained too long? I'd imagine some apps are more prone to this than others.

30 minutes should be tops for an oil change done by yourself after you've started the draining process.

 

[asiancivicmaniac]

If there are particles that are big enough to precipitate out, shouldn't the oil filter have caught it?

 

[08_SHELBY]

Originally Posted By: asiancivicmaniac
If there are particles that are big enough to precipitate out, shouldn't the oil filter have caught it?
Debris and heavy stuff? Im with you, the filter should have done its job on stuff and debris already.

 

[sciphi]

Changing the oil on a warm engine helps the MityVac suck it out easily.

 

[demarpaint]

Change it warm, dirt is in suspension, oil flows better, especially when its cold out.

 

[wag123]

IMHO it doesn't make ay difference either way. Any good oil filter will have trapped 99% of what could have settled and the remainder is held in suspension by the oil for a much longer period than just overnight.
Personally I drain it cold because I'm not going to stick my hand under the hot exhaust manifold on my Toyota to deal with the oil filter.

 

[SteveSRT8]

The whole change it warm thing is to have the engine well lubricated for the dry restart. Most people put the filter on empty and thus you wait a few seconds for oil pressure.

 

[tommygunn]

I personally like the engine cold, because I don't like getting my hands and arms burned. I get a cold engine start it up to get a little oil on everything then back it out of the garage to my spot that I like to change the oil. I tried changing it one time when it had sit overnight without starting and you could hear the metal to metal sound until the oil filter filled up and started reaching crucial parts.

 

[KrisZ]

I changed oil hot, warm or cold depending on the circumstances. I noticed that it makes little difference in flow, unless it's well below freezing outside. The amount of oil that comes out is also the same, as with cold changes all of the oil is already drained in the pan. As far as stuff settling on the bottom of the oil pan, I think the issue is highly exaggerated. I poured out oil jugs filled with used oil that sat for months and, surprisingly, there was a fairly small amount of contaminants that settled at the bottom of the jug. So unless you have a diesel engine or a poorly maintained gasser, there will be very little contaminants sitting at the bottom of oil pan after 8-12 hour period.

Also I am not going to waste 30 minutes of my time just driving around to warm up the car. If I have to go somewhere before the OC, then the oil is changed hot, otherwise it will be changed cold. That's my

 

[Pop_Rivit]

In my opinion, no, there's no benefit to changing it hot.

If there is significant debris in the oil you have a bigger problem than an oil change will fix. And, hot or cold, there is still a fair amount of old oil inside the engine that stays there until it starts circulating.

When I change the oil in my vehicles they get no more of a warm up than moving them 100' from the garage to my shop building. If I know I'm going to change the oil ahead of time I might have them all in the shop, with one ready on the lift the evening before.

I don't (and won't) change it in extremely cold weather. If it's that cold out and I need to change the oil I'll get the shop nice and warm. But that's a rare event-most of my oil changes are at 6 months (warm spring day and a warm fall day) irrespective of the mileage.

 

[Scum_Frog]

Originally Posted By: KrisZ
I changed oil hot, warm or cold depending on the circumstances. I noticed that it makes little difference in flow,


Same here!

 

[SevenBizzos]

I prefer changing the oil when warm because it's a lot easier to take the filter off when it's warm.

During the winter an added benefit is opening the hood and letting the engine warm the garage a bit before I work in there.