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Oil Changes, Hot vs. Cold


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I was going to post this in another thread about what oil type to use but that thread was really spread pretty thin and I see that you guys were pretty tired of it.

 

So, I came across this article a long time ago and found it very interesting to say the least. It's like anything in this world there are varied opinions for a lot of subjects. Keep and open mind and read this article and see what you think. I was one that would always warm up an engine before draining the oil, but I've reconsidered that old myth if you will.

HotorColdOil.pdf

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Thanks for sharing Kbear. Thats a great article. Often wondered about the benefits of oil drain while the engine warm to get better flow as opposed to a longer time with a cold engine to get most of it returning to the sump.

A cold engine drain over a longer time is the better way to go. Interesting.

 

However if you're using a high quality oil with regular changes, the small amount of old oil left in the sump will not matter Jack shite. (Woops - Jack shit, Aussie for meaning, Insignificant).:fing02:

 

 

IMG_1123(1).PNG

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Well that was a good read, thanks for sharing. Looks like I'll be doing cold oil changes from now on, the "warm" left-behind value of nearly 7% sucks.

 

I wonder why the manufacurers suggest doing them warm/hot? Maybe there is some merit in that for getting more sediment in suspension in really old oil?

 

I checked the manuals for my Yamaha (warm it for several minutes first), Vespa (the engine must be hot) and my Hondas (the instruction is to have the engine "warm"). So they are quite consistent but at odds with the article. 

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I can't get the article to download on my device,  just looking at the portion,  above.  Does it go in to why the warm volume is lower?

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32 minutes ago, Cogswell said:

I can't get the article to download on my device,  just looking at the portion,  above.  Does it go in to why the warm volume is lower?

Nothing more complicated than the drain time allowed! And that the warm oil didn't flow back to the sump as fast as the hot oil.

The cold drain was 12 hours after getting the engine to the Hot state.

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1 hour ago, Grum said:

Thanks for sharing Kbear. Thats a great article. Often wondered about the benefits of oil drain while the engine warm to get better flow as opposed to a longer time with a cold engine to get most of it returning to the sump.

A cold engine drain over a longer time is the better way to go.

The oil drain table says it all.

 

However if you're using a high quality oil with regular changes, the small amount of old oil left in the sump will not matter Jack shite. (Woops - Jack shit, Aussie for meaning, Insignificant).:fing02:

You're very welcome for the article. I found it very interesting and thought you guys should have the opportunity to put your eyeballs on it. Like I mentioned I've always subscribed to heating up the engine first then draining the oil. Now, I can confess, and this is the truth I've often thought in the back of my mind "Does it really need to be hot?" After all I'm not in a race when I'm draining the oil so why in the world would I need it to drain really really fast? Now, and over several oil changes on several different motorcycles now, I'm really into turning on some music, having a glass of ice tea (or whatever you prefer to drink) and just taking my time changing the oil and filter. I'm just NOT in a huge hurry. :woohoo:

 

1 hour ago, Terry said:

Well that was a good read, thanks for sharing. Looks like I'll be doing cold oil changes from now on, the "warm" left-behind value of nearly 7% sucks.

 

I wonder why the manufacurers suggest doing them warm/hot? Maybe there is some merit in that for getting more sediment in suspension in really old oil?

 

I checked the manuals for my Yamaha (warm it for several minutes first), Vespa (the engine must be hot) and my Hondas (the instruction is to have the engine "warm"). So they are quite consistent but at odds with the article. 

You're welcome also for the article indeed. Glad you found it worthwhile. Yes, it's not going to hurt you to change the oil when it's cold. You can take comfort in the fact that you are indeed getting rid of more contaminants in your oil drain than you would by heating it up and distributing those contaminants throughout the engine and not draining them as you should. Just think, now you don't need to spend time warming up the engine only to have to deal with hot oil when you drain it. All that to get it to drain faster. Are you part of a pit crew???? 

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Interesting, but I'll still stick to hot oil changes. I don't put the plug back in as soon as the oil stops coming out in a steady stream, which is

basically what they did. Mine usually sits for an hour or so to drain as much as possible. I mean it makes sense that you'll get less oil out if

you don't give the oil time to drain down from the upper end. There's a reason they tell you not to check the oil immediately after shutting

off the engine. I use a Fumoto drain plugs on my 4 wheel vehicles and they usually sit at least a half hour before I shut off the drain, just to

let as much oil as possible drain down.

 

I wonder what the results would be if they had given each an hour, or even a half hour to drain. Thanks for posting that article up.

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Major variable in article is NOT hot vs. warm vs. cold oil. It's drain-time!!! If they had left hot & warm oil to sit for 12-hrs, it too would've drained just as much, if not more!

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No car has ever detonated due to choosing hot vs. cold oil changes.  They do fail when you forget to change the oil though.  🙃

 

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I’m a hot oil changer. Being a generator tech having worked all over the world and not always being offered a choice between Cold Warm Hot changes more often it was always hot. Walk up, shut the unit off and get to work, 20 deg F  or 120 deg F outside, didn’t matter, you just did it. I’d say in my own experience over the years I get more oil out hot than cold, no doubt about it. 
 

As long as I’m the one doing the services I’m doing it hot. But that’s just me. 

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Great article, thanks for sharing. However, the drain time was only 4 minutes in the test protocol.  I am with DannoXYZ, if the drain  time is longer,  the hot /warm oil amount will be the same or higher. If a paid mechanic changes the oil, then time is money. When I change it, I let it the hot engine/ warm engine sit for 10 minutes or so and then let it drain for 15-30 minutes while checking around the bike/car.

In any case, this article is a great reminder in regards to checking my train of thoughts again.

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In all these cases over 90% of the fluid is replaced.  It resets not just viscosity but the main "worst" things about old oil, like acidity and whatnot.  It is interesting but I would not go out of my way to do hot or cold.

 

Agree that for most industrial applications, hot changes are directed.  But a lot of those procedures were written "way back when" and it's just how things continue to be.  On a related example, the procedures for breaking in large diesel engines look just like how we did it in the 60's and don't reflect modern tribological studies, which shows that for modern, plateau honed cylinders, "break in" is done really quickly (rule I recall is 80% of lifetime wear in first 21 minutes) and doesn't matter like we used to think it did.  But we still do it that way anyway, because "it's always worked."

 

It's also worth mentioning that for most large engines, they do condition based oil changes based on test results vs. intervals, and they sometimes have attached things like oil purifying circuits and whatnot.  On small engines like cars and trucks we are changing oil relatively early, so 90% change out is good enough.

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Oh yes........ another solution for a problem that doesn't really exist??

IF you could drain ALL the oil it says in the manual for an oil and filter change, you're more than good.... drain time....

Note there is an additional volume of oil required should you rebuild and have a virgin engine...... you will never drain that out, so you're worried about a little oil left in?  On an FJR it's a full litre.....

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52 minutes ago, raYzerman said:

Oh yes........ another solution for a problem that doesn't really exist??

IF you could drain ALL the oil it says in the manual for an oil and filter change, you're more than good.... drain time....

Note there is an additional volume of oil required should you rebuild and have a virgin engine...... you will never drain that out, so you're worried about a little oil left in?  On an FJR it's a full litre.....

 

Agreed, raYzerman. A solution in search of a problem. A little bit of old oil left is no big deal IMHO. The biggest issue I've seen is shops consistently adding too much new oil. I've had to siphon oil out after service. Excess oil:

 

IMG_6232.thumb.JPG.7634b12ef7f47fb9e3df22291a58d6a0.JPG

 

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Changing oil hot doesn't make much sense when you think about it (when not in a time crunch). What is the advantage of changing the oil when it's hot/warm? It will flow through the engine and drain faster right? Well guess what? That's what the oil is going to do whether you pull the drain plug or not. :laughing6-hehe:

Changing cold just means you didn't sit there for 20 minutes waiting for the oil to flow into the oil pan.

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Changing oil hot means that nothing has had the time to drop out of suspension, the water is not condensed onto various metal parts, and it flows easier as a bonus.

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Wonder if they change this engine oil hot or cold...

 

Kec42V0.jpg

crank.jpg

pistons.jpg

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Have to be Hot........that thing would take 6 weeks to cool down! Can't wait to see the frame, wheels etc. arrive, gonna be an awesome bike.:laughing6-hehe:

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57 minutes ago, RC1237V said:

Wonder if they change this engine oil hot or cold...

 

Kec42V0.jpg

crank.jpg

pistons.jpg

Since most of it is in a service tank...it's less hard than you'd think.  The other thing is big engines like these have jacket water heaters.  We keep them warm (not operationally hot) when they are in standby, and prior to starting them.  I am trying to remember, I don't remember if it was prescribed to change oil at temperature or not.  But I'm really draining far more out of the service tank and sump than I am the engine, it's an even smaller percentage that we would pull out.  And again...goes through a purifier, etc.

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LOL Grum beat me to it... can't wait to see the engine swap to get that in a VFR!  Only q is what gen it fits best in...

 

based on the dimensions, I'm thinking air cooled

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4 hours ago, FJ12Ryder said:

Changing oil hot means that nothing has had the time to drop out of suspension, the water is not condensed onto various metal parts, and it flows easier as a bonus.

The oil has polymers that absorb the water.  That's the white layer floating on top of your oil when it's cold.  When I used to park my bike under cover but outside in NorCal, it often had condensate.

 

When the oil heats up, the water is released quickly evaporates.  Crank case vacuum (if so equipped on a big engine) or a breather tube will get it out pretty quickly.

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Just now, rhoderage said:

LOL Grum beat me to it... can't wait to see the engine swap to get that in a VFR!  Only q is what gen it fits best in...

 

based on the dimensions, I'm thinking air cooled

Sea water cooled!  😎

 

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