How long to run engine [or not] before draining??

[440Magnum]

Originally Posted By: grndslm


Perhaps taking off the filler cap and "loosening" the dipstick on an engine that's been sitting overnight would get more crud than a warm engine with the filler cap on.


Doesn't make any difference whatsoever. Engines have an air inlet for the PCV or CCV system, which will feed 50x more air per second into the crankcase than it would take to begin to pull a vacuum by draining the oil. Removing the oil cap or dipstick will have ZERO effect.

 

[Quattro Pete]

I always change my oil on a hot engine, right after I got back from running errands or taking some other trip. Because I use an extractor (via dipstick tube), it really helps to get it sucked out quicker when the oil is warm. The extraction tube is fairly narrow, so cold thick oil wouldn't travel through it very well.

 

[Rand]

I like to warm mine up either with a 20-30mile trip

or If I'm in a pinch I'll just let it idle for 15min.

the oil doesnt need to be 200F

Its fairly amazing how much thinner the oil is from 30F to about 100F

 

[Coprolite]

Taking the fill cap off while draining doesn't hurt at all. It also provides a visual queue that work is underway and reduces the chance of someone closing the hood and trying to move the vehicle.

After all, the cap will have to be removed to add oil in either case.

 

[Gabe]

Cold.

The oil takes a while to drain down to the pan - which is why you should not check your oil when the motor was just ran.

 

[SLCraig]

Ideally my car sits for a while before I change it.
I just usually crack the plug on a cold engine that has been sitting overnight and drain it.
All the oil when hot has drained down since last it was parked anyway, so I figure its nicer to work with a cold engine than a hot one. Been doing it this way since I have been changing my own oil. Sometimes I don't have time so I do it hot, but that is rare.

 

[Garak]

Originally Posted By: SLCraig
I just usually crack the plug on a cold engine that has been sitting overnight and drain it.

Another reason I do it hot is simply out of habit. Doing a cold oil change on a taxi is just about impossible, unless you deliberately park it for several hours, which defeats the purpose of owning taxis.

 

[Umibozu]

My rating on the topic would be(best to worst)
1) Hot, right after city or highway driving
2) warmed up, idling for a few minutes
3) cold, sat overnight and just pulling the drain plug.

My justification would be that the hotter more viscous oil flows faster, therefore able to pick up more sediment due to higher fluid momentum.

 

[TFB1]

Originally Posted By: Umibozu
My rating on the topic would be(best to worst)
1) Hot, right after city or highway driving
2) warmed up, idling for a few minutes
3) cold, sat overnight and just pulling the drain plug.

My justification would be that the hotter more viscous oil flows faster, therefore able to pick up more sediment due to higher fluid momentum.


Any sediment should be in the filter, otherwise I agree...

 

[fdcg27]

Originally Posted By: Donald
I think you want it warm to hot so it pulls the most [censored] with it as its draining. Thats the point of it being warm to hot. Not to drain faster.


Of course.
No need to idle the car or go for a drive, as some have posted.
Just drain it when you get home from work or weekend errands.
I've done this for years.
No sense wasting fuel just to warm the oil.

 

[Umibozu]

You would be surprised how much sediment actually sits in the bottom of the pan.

 

[TFB1]

Originally Posted By: Umibozu
You would be surprised how much sediment actually sits in the bottom of the pan.


No surprise here because I've never found any in my engines I've had apart... If it's big enough to see, the filter will catch it, IF it's doing it's job...

Something that been neglected, well that may be a different story...

Sometimes a little sludge, bit of a gasket, etc will find it's way into one of the corners and just set there, hot or cold it usually doesn't usually drain out with the oil...

 

[bigt61]

I've drained mine hot or cold. I've never warmed it up just to drain it, but if you're pulling it onto ramps and have to start a cold engine, it might not hurt to get the oil a little warm. Probably not a big deal either way.

 

[Umibozu]

Originally Posted By: Umibozu
You would be surprised how much sediment actually sits in the bottom of the pan.


No surprise here because I've never found any in my engines I've had apart... If it's big enough to see, the filter will catch it, IF it's doing it's job...

Something that been neglected, well that may be a different story...

Sometimes a little sludge, bit of a gasket, etc will find it's way into one of the corners and just set there, hot or cold it usually doesn't usually drain out with the oil...

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Again I disagree. Even well maintained cars will have sediment in the pan that gets drained out with the oil that the oil filter does not catch. Remember the oil filter is only efficient up to a certain micron level. Most particles smaller than the micron rating will simply pass through. This is what I'm referring to as sediment at the bottom of the pan. I've taken only three motors apart in my life but everytime i cleaned the oil pan with a rag I see the sediment clearly on the rag. Another observation some one will see is at the bottom of the oil catch pan. Every time I pour the recently drained oil from the oil catch pan to a used oil container I can visually see some of the sediment still sitting on the bottom of it. I usually try to wipe my oil catch pan after every oil change to keep it clean. The sediment has the consistency of a buildup of small dust particles in the oil.

For you to suggest the sediment I observe is due to an under maintained car is a low blow, and being a bitoger I take offense.

To the OP, the warmer the oil prior to drain the better IMHO.

 

[Coprolite]

Umibozu, I fixed your post for you.

Originally Posted By: Umibozu
My rating on the topic would be(best to worst)
1) Hot, right after city or highway driving
2) warmed up, idling for a few minutes
3) cold, sat overnight and just pulling the drain plug.

My justification would be that the hotter less viscous oil flows faster, therefore able to pick up more sediment due to higher fluid momentum.

 

[Umibozu]

Originally Posted By: Coprolite
Umibozu, I fixed your post for you.

Originally Posted By: Umibozu
My rating on the topic would be(best to worst)
1) Hot, right after city or highway driving
2) warmed up, idling for a few minutes
3) cold, sat overnight and just pulling the drain plug.

My justification would be that the hotter less viscous oil flows faster, therefore able to pick up more sediment due to higher fluid momentum.


Thanks!

 

[SS1970chrysler]

Except when doing a UOA, I rather drain mine colder. I've had many engines knock at first startup after a change+fill if the oil was hot, but none did so if drained cold. IMO, the knocking would do more damage than some miniscule sediment that didn't drain.
Letting a hot engine sit for an hour or two before draining is also a good alternative. Many of my car owners' manuals recommend pulling the coil wire and cranking the engine before starting to avoid this knocking. Changing the oil colder is just easier.

 

[Clevy]

Originally Posted By: Darren270
I take it for a spin on the highway...letting it get up to temp and then head home. Let it sit for about 10 mins and then pull the plug. The oil is pretty dang hot so I wear gloves when I do this.


That's basically how I do it. Then leave it to drip for a half hour before putting the plug back in. I also remove the oil filter so the top end back drains into my drain pan. In my mind the oil is completely evacuated and ready for new stuff.

 

[Clevy]

Originally Posted By: Gabe
Cold.

The oil takes a while to drain down to the pan - which is why you should not check your oil when the motor was just ran.


Absurd. Since the engine in operation has oil distributed throughout then that's when it's most important to check it.
If the oil is a bit high at start up cold but perfect in operation then that's ideal,not perfect when cold then low when in operation.
Just my opinion.

 

[TFB1]

Originally Posted By: Clevy
Originally Posted By: Gabe
Cold.

The oil takes a while to drain down to the pan - which is why you should not check your oil when the motor was just ran.


Absurd. Since the engine in operation has oil distributed throughout then that's when it's most important to check it.
If the oil is a bit high at start up cold but perfect in operation then that's ideal,not perfect when cold then low when in operation.
Just my opinion.


If it's COLD and only run for a couple minutes you can bet on a very low reading because much of the oil is yet to drain back into the pan, depending on ambient could take 30 min or more...

ALL engines I've seen will read two or more quarts low if the level is checked with the engine running... You also have to be quick about it, as the splash off the crankshaft usually slings oil to the point the dipstick enters the crankcase, giving a reading that can be 3x or more of normal...

I never really worry about level, if it's a quart down I add, if not I leave it alone...