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

[grndslm]

I've always run my engine for a minute or two to get the oil SOMEWHAT less viscous and expecting it to drain smoothly. And, I expect this doesn't get it as thin as would be preferred, so I typically take my time and let it drip for a while. Sometimes I feel like if I put the oil pan bolt back in there and then come back in 15, the drops will create a larger surface tension (??) with other drops and all fall out at the same time. Not a whole lot, but every little bit counts, right?

But I'm wondering now, does anybody drain their engine after it's COMPLETELY cold? I've heard that there can be like a 1/4 of a quart difference measured between a hot and cold engine. So... perhaps in my example above, if I left the car there to cool down overnight, there would be another 6 ounces of black oil that comes out??

 

[JAM25]

What I do is drive around until it gets to normal temp. Get the oil nice hot. You'll build a better flow plus everything will slide off when u take the plug out. I think its a better way to do the oil change but thatds just my opinion.

 

[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.

 

[Falken]

Nice and hot is the way to go. The hotter the better.

Take off the oil fill cap and pull the dipstick so it really drains quick, to pull any sediment at the bottom of the pan with it hopefully.

Careful though, this is where messes happen!

If you want to be sure you do a clean job, don't open the oil fill cap or pull the dipstick tube, it won't drain quite as fast.

 

[grndslm]

Originally Posted By: Falken
Take off the oil fill cap and pull the dipstick so it really drains quick, to pull any sediment at the bottom of the pan with it hopefully.

Dang, that's a slick idea Falken. I'll have to try that.

Thanks for the tip!

 

[Pop_Rivit]

I think you'd be hard pressed to find much of a difference in the quantity that gets removed. You also have quite a bit of oil that is still in the engine either way. The reality is that the small amount of old oil that's in the engine when it's drained (either hot or cold) is meaningless.

If you have "sediment" at the bottom of an oil pan there are bigger problems than an oil change will correct-there should be anything there in the first place, and if there is it should be picked up by the oil filter.

And yes, I almost always change mine cold, or when it's only been driven the 50' or so from the garage to my shop building.

 

[d00df00d]

Originally Posted By: Pop_Rivit
I think you'd be hard pressed to find much of a difference in the quantity that gets removed. You also have quite a bit of oil that is still in the engine either way. The reality is that the small amount of old oil that's in the engine when it's drained (either hot or cold) is meaningless.

If you have "sediment" at the bottom of an oil pan there are bigger problems than an oil change will correct-there should be anything there in the first place, and if there is it should be picked up by the oil filter.

This is pretty much what I was going to say.

 

[Zaedock]

Realistically, it doesn't matter. If you do it cold, you’ll probably get more out as it had all night to drip into the pan.

If you’re doing a UOA, hot is the way to go.

 

[tc1446]

With all the thin oil we use these days it runs out like water anyway.

 

[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.

 

[callbay]

Any chance of hot being better as crud on the engine surfaces would more likely get in the oil and therefore be drained out. Draining cold the crud would stay on the engine surfaces more and not get drained out.

Any thoughts?

 

[grndslm]

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.

I would think draining faster and pulling more crud go hand in hand.

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.

 

[SwampSurvivor]

I usually drive the 70 mile trip to my parents (so it's well up to temperature), get it up on the ramps immediately and start draining.

 

[Garak]

Originally Posted By: tc1446
With all the thin oil we use these days it runs out like water anyway.

Okay. I'll park my truck outside in -40 overnight, then start it and pull it into my heated garage. You go in and pull the plug and see if the oil runs out like water.

I almost never change the oil when cold, unless it's "necessary" for some reason. And I've done Falken's trick of pulling the dipstick and/or the fill cap prior to draining for many years. I don't know if it's accomplishing much on every engine out there, but there's something to be said for speeding up the draining as possible.

And Falken, without a Fumoto, I make a mess no matter what I do, cap/dipstick out or not.

 

[TFB1]

Removing the oil cap isn't going to cause a problem but it isn't likely speeding up the process either, all engines have some type of fresh air pickup routed back to the air cleaner, it isn't a sealed system...

I drain mine hot and have for almost 47 years, chances I'll deviate now is about zero...

 

[Garak]

I've noticed a difference in speed in a couple engines, but like I mentioned, I doubt it would be a major deal in every engine out there. From what I've seen, it doesn't make a sliver of difference in my G, but I do it anyway out of habit. My approach to a quick drain is to make sure the oil's hot in the first place. That'll be the biggest determining factor.

 

[TFB1]

Originally Posted By: Garak
I've noticed a difference in speed in a couple engines, but like I mentioned, I doubt it would be a major deal in every engine out there. From what I've seen, it doesn't make a sliver of difference in my G, but I do it anyway out of habit. My approach to a quick drain is to make sure the oil's hot in the first place. That'll be the biggest determining factor.


Yup, no doubt...

 

[d00df00d]

If I just happen to be driving before I do my oil change, then I do try to open the drain plug ASAP. Even if the difference is minor, it's worth having for minimal effort.

If the car is cold, though, I'd rather just let it drain for 5-10 more minutes than spend that time warming it up so it'll drain faster. This is especially true because I do oil analysis at every oil change, and I don't want to make my fuel dilution look higher than it is.

 

[05LGTLtd]

I've never loosened the oil cap, but I really can't imagine hot oil coming out of a Subaru pan any faster than it does already. That [censored] is coming out sideways already...

 

[440Magnum]

Originally Posted By: grndslm
I've always run my engine for a minute or two to get the oil SOMEWHAT less viscous and expecting it to drain smoothly.


IMO, that's the worst possible way to drain.

Either drain HOT, so that the oil is at its thinnest and any sediment is circulated...

or drain COLD, so that at least all the oil will have run down into the pan right after the last hot shutdown, and though it might be thick it doesn't have to drain out of all the upper end of the engine.

A quick start without a full warmup pumps cold oil up to the top of the engine, so now when you shut down and drain, the cold oil has to work its way all the way down from the top end.