Oil Changing, Engine Hot or Cold???

[IH POWER]

Has anyone else ever drained the oil and put the plug back in and dumped a coupe quarts of diesel fuel in the crankcase and ran it for a few seconds? I have. Sure cleans out the gunk.

 

[Dieselcrawler]

Hot engine. Punch hole in filter, remove plug. Grease entire truck and look over brakes and driveline. Check fluid in rear and trans(manual). By this point it is done dripping and reinstall plug and new filter. Refill. Way I do all my rigs and busses at work

 

[PwrSmoke]

I must be missing something here.

How do all the varnish causing agents know ahead of time I'm going to change my oil so they can avoid draining to the pan in anticipation of wreaking havoc in my engine? I'd like to get more of the used oil out of the engine, not less and I imagine a lot of it is clinging to the inside of a recently ran engine. Which to me means a long wait for it to get to the pan and I don't think that oil draining to the pan knows whether or not the drain plug has been removed from it. Seems to me that when the engine sits overnight, the amount of oil in the oil pan approaches maximum which would mean the amount of varnish producing agents and contamination left in the engine is at a minimum. Albeit we have thicker oil clinging to the smooth walls of the oil pan but I doubt the volume of that would compare to the warm oil clinging to the rest of the mostly rough cast block.

The only argument I can think of against that is that a recently ran engine has the maximum amount of contaminants suspended in the oil and not sitting in the bottom of the pan where they might not be carried out by the oil as it drains.

When you guys change it hot, how long do you really let it drain? Until the last drip, until it starts dripping instead of a stream, until the thick stream becomes a thin stream, OR, once you're done changing the filter and wiping the 15w40 out of your ear and armpit? I think I am going to try the last next time I change, hot, then put the plug back in and see how much oil ends up in the pan a few hours later.

Frame of reference alert: It doesn't really get COLD where I live so I have no experience draining oil wearing insulated carhart coveralls.

Not to single anyone out but Blackstone recommends a hot sample to "...help cook out any normal moisture or fuel build-up."

Anyone know how much oil is left in the oil cooler? Probably a waste of time worrying about ounces when there are pints that are never coming out during a change.

In their early life, oxidation products are "soft" and temperature sensitive. Think of bacon grease in the pan after you've fried the bacon. When you first turn the stove off it's clear and liquid and easily pours out of the pan. Let it sit a few hours and it starts to congeal and stick in the pan. Or to the sides of the oil pan when you leave a truck sit overnight. Even changing the oil cold, you are getting some of them but if they stay in the engine, the stuff gets harder and sticks more. It's a slow buildup and you want to get more of them in the early stage. Warm oil changes does that.

And, yeah, we can be realistic and say hot or cold may not matter every time. Depending on your OCI, how the truck is driven and the types of oil filtration used, you may or may not have a large buildup of oxidation byproducts. Since it's not likely you will know ahead of time, isn't it better to take proactive steps to make sure you get them out?

Another "and yeah," would be that if you live in an area that's "warm" maybe it doesn't matter. Nothing I've read states the actual temps required to keep the oxidation byproducts in solution. Maybe an 80 degree day is enough? Don't know. What I do know is that people who know a whole lot more than me recommend changing the oil hot and we've discussed only a few of the reasons why.

BTW, you are interpreting "draining hot" too literally, I think. You don't have to drain 200 degree oil out and frenchfry your hands in the process (unless you like the smell of frenchfried hands in the morning ( : < ). A hot engine takes a minimum of 15 minutes for the hot oil to drain down from the upper end. The oil will still be pretty warm in an hour and within an hour, the upper end is very well drained. So, letting the engine cool for an hour makes the process more comfortable (if comfort is key) and it gets the job done as far as draining the oil warm.

 

[whiteboyslo]

Cold, as in at least a couple hours of non-use. It's bad enough I rarely (if ever) change the oil on anything without making a mess. I don't need scalding fluid added to the equation. If/when I ever have an engine fail on me and if/when I can attribute its demise to my unwillingness to change the oil while hot, I'll let you know.

Mike

 

[hesutton]

I don't think anyone pulls a trailer up and down a mountain, then races to the garage and immediately pulls the drain plug and filter with the oil boiling hot. That's insane. Warm, not burn your skin hot. And, no..... you don't turn off the key and immediately pull the drain and filter. Of course it needs to sit for a half hour or so to let the top end drain. And if you think you can get all of the old oil out by doing it cold, that's just not reality. No matter what you do, up 20% of the oil will remain in the engine during an oil change. If you've ever pulled one of these IDI's apart for a rebuild you know exactly what I'm talking about.

By the way......... It's just an oil change......... not a NASA launch..... It seems this is just as personal, and as touchy a subject as oil brand preference.

Heath

 

[Mulochico]

My owners manual (yes, the p/o still had it ) says to fully warm up the engine, then shut it off for 20 minutes before checking the oil level. Reasoning is warm oil is already expanded as much as possible, and all the oil that will should drain back into the pan in 20 min. So I take it for a drive, let it sit for a bit, replace the filter, then drain the pan until it is barely dripping anymore (lubing the truck as I wait), add oil (11 qts., add any needed after warm-up/20 min wait).

Total time 20 min+/-. No hurry, just thorough.

 

[Agnem]

I change mine while the engine is fully hot, and just shut down. I use an SHA drain hose assembly from CAP Oil Change Solutions (http://www.oilchangesystems.com/products/hose-assemblies/#hose2) to do oil changes on most of my rigs. Each one is permanently fitted with the hose. Far better than anything else, you never mess with a drain plug, spilled oil or hot oil on your skin, and if it were not for the oil filter, you would never have to crawl under the truck. I just hook up the hose to an old eagle can, and put a vacuum on it with an old 220V vacuum pump scavenged from an IBM Mainframe reel to reel tape unit. The can fills up, and I know my oil is changed when I can hear the vacuum in my oil fill. I just start the pump, and go have dinner or whatever, and come back to a cool truck and a hot can of oil. The drain hose forms the return line for my FS-2500 bypass filter as well, so that gets emptied too.

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[whiteboyslo]

Of course it needs to sit for a half hour or so to let the top end drain. And if you think you can get all of the old oil out by doing it cold, that's just not reality.

Why? Does it magically go BACK up the engine? Once it's drained into the pan, it's there. Unless you're running Crisco, it's gonna come out.

No matter what you do, up 20% of the oil will remain in the engine during an oil change.

My thoughts exactly, hence why I don't go through all the extra hoops. Nothing's going to drain the inside bone dry, not that you really want that anyway.

By the way......... It's just an oil change......... not a NASA launch..... It seems this is just as personal, and as touchy a subject as oil brand preference.

Word.

Mike

 

[hesutton]

Why? Does it magically go BACK up the engine? Mike

Yes, it is magic!







No, the point I made was the next sentence about "up to 20% will remain in the engine" stuff.


Heath

 

[Agnem]

I'm going to say that 20% is too much to speculate is still in there. Back in the day, I put 10 quarts in, and if I emptied the filter, I could darn near get 10 quarts out. This is when I used to put the used oil back in the bottles the new oil came out of. There may have been a half a cup missing, much of what I attributed to just spilling some of it. Yes, there will always be a coating. That, and the part that the drain plug threads into sits above the bottom surface of the pan, so there is no way to get the last 5 or 6 tablespoons out. The soot is a heavy deposit, and sticks like crazy to everything, so our engines never run with clean oil for more than 15 minutes. But, that said, it's always helpfull to get whatever deposits are willing to come, out, while the oil might still have them in suspension.

 

[IH POWER]

Hey mel would it hurt to put a rachet on the crank bolt and turn it over like half a turn? That might get some of the oil left in there out.

 

[icanfixall]

Once the pan is emptyed I don't think hand cranking the engine will push out any more oil. Maybe it will push out some thats in the lifters but thats about it. I really don't think it will change anything. Mel makes a good point about what he has gotten out of these engines during an oil change... Leaving up to 20%... I don't feel thats accurate. Leaving 20% in there is around 2.2 quarts. On an 11 quart oil change..

 

[PwrSmoke]

Might be close to 5 percent on a new engine. Like Heath said, I recently noted how much oil was in the engine upon teardown (and WEEKS of draining on the stand) and that it took a little extra oil on the first fill to bring =it up to the mark. On an oil change, I doubt it's even a full percent left in the engine.

 

['94IDITurbo7.3]

could always drain the oil then start the engine up to pump the rest of the oil out of it........





































JUST KIDDING!!!! DO NOT DO THAT!

 

[whiteboyslo]

could always drain the oil then start the engine up to pump the rest of the oil out of it........

Just make sure to flush it out with water after.........

Mike