Cold engine oil changes...

[Top Ten]

I've been changing oil in cars, trucks, motorcycles, lawn mowers, garden tillers, etc. for close to 50 years now. And I have always done it with a hot/warm engine. I did oil changes hot because the oil was thinner and would drain more completely, and any particles in the oil would be suspended and would come out with the old oil. But after reading up on oil viscosity, multi-grades oils, how multi-grade oils change viscosity with polymer additives, I have come up with a hypothesis.

Multi--grade motor oils, say 10W40 for example, have a viscosity of 10 at cold temperatures and 40 at operating temperatures. The polymer additives expand with heat and cause to oil to thicken at operating temperatures. I think the technical temps are 0 degrees F cold and 200 degrees F hot. Based on that information, the oil should actually be thinner cold than it is hot. Or at least flow just as well cold as hot. Right?

Making the assumption that cold oil is as thin as hot oil, what is wrong with doing oil changes cold? If the oil is thinner, it should drain out as fast or faster than out of a hot engine. With a cold engine, all of the oil is already in the crankcase or oil tank, where, with a hot engine, you still have oil in the upper reaches of the engine that need to drain down to the crankcase. As to suspended particles in the oil, with modern machining tolerances and good filters, there shouldn't be many particles in the oil. And how many of us have gotten hot oil on our hands, held hot parts, or been burned by touching a hot engine part? And a cold-engine oil can be done anytime; no need to ride first or bring the engine up to operating temp.

In summary, I am suggesting cold-engine oil changes may be better than hot oil engine changes because they are (1) Just as fast or faster, (2) more complete, (3) safer, and (4) more convenient (no warm-up time needed).

Go ahead. Tell me why I am wrong.

 

[RCinNC]

No one needs to tell you that you're wrong; if you proposed the hypothesis, it's simple enough for you to test it and form your own conclusion. Do two oil changes; one with the engine warmed up to the correct temperature specified in the operator's manual, and one totally cold. You proposed four reasons why you believe a cold change is better, and three of them are simple to evaluate:

1) Just as fast or faster: That's simple enough to check. Set your standard for what constitutes "totally drained", and then time each oil change to see which takes longer.

2) More complete: If you define "complete" as the maximum amount of oil you can drain from the engine in an oil change, then that's simple enough; just measure the amount you drain from the engine during each change. The container with the most oil wins.

3) Safer: if "safer" means "less chance of being burned by a hot engine", then yes, I'd say changing the oil on a cold engine is safer.

4) More convenient: that's too subjective to define. If the task is convenient but inefficient, then the convenience is moot. It may be convenient to drain a cold engine, but if the amount of old oil you remove is less than what you remove from a hot engine, then the convenience is kind of pointless because you haven't removed as much of the old oil from the engine as possible, and that's the whole point of the exercise.

 

[VRODE]

I don't think you're wrong.
Oil weight may have a little to do with it, and my 5W-40 flows fine cold. The residual amt in the engine will go thru a new filter anyway. I'm sure some believe draining it hot is better. I can't say they're wrong, but Imma change my oil as I see fit. So there.

 

[Eville Rich]

The issue is the oil viscosity at different temps. Let's take 10w-40. When cold, its viscosity is that of a 10 and when hot, that if a 40. However, the viscosity of a 40 when hot may be less than that of a 10 when cold. There are two variables to consider - the viscosity of the oil rating AND and the temperature. There are charts available that show this relationship. For 10w-40 the hot viscosity is still lower than the cold viscosity, and therefore flows more freely.

I'm not going to debate the relative merits of hot or cold oil changes. The main thing is to just change the oil. After that we're really nipping at the margins. I generally do mine when the engine is warm, but it depends on the engine and how I'm feeling that day. Not going to lose sleep over it.

Eville Rich
2016 S10

 

[Jlq1969]

I've been changing oil in cars, trucks, motorcycles, lawn mowers, garden tillers, etc. for close to 50 years now. And I have always done it with a hot/warm engine. I did oil changes hot because the oil was thinner and would drain more completely, and any particles in the oil would be suspended and would come out with the old oil. But after reading up on oil viscosity, multi-grades oils, how multi-grade oils change viscosity with polymer additives, I have come up with a hypothesis.

Multi--grade motor oils, say 10W40 for example, have a viscosity of 10 at cold temperatures and 40 at operating temperatures. The polymer additives expand with heat and cause to oil to thicken at operating temperatures. I think the technical temps are 0 degrees F cold and 200 degrees F hot. Based on that information, the oil should actually be thinner cold than it is hot. Or at least flow just as well cold as hot. Right?

Making the assumption that cold oil is as thin as hot oil, what is wrong with doing oil changes cold? If the oil is thinner, it should drain out as fast or faster than out of a hot engine. With a cold engine, all of the oil is already in the crankcase or oil tank, where, with a hot engine, you still have oil in the upper reaches of the engine that need to drain down to the crankcase. As to suspended particles in the oil, with modern machining tolerances and good filters, there shouldn't be many particles in the oil. And how many of us have gotten hot oil on our hands, held hot parts, or been burned by touching a hot engine part? And a cold-engine oil can be done anytime; no need to ride first or bring the engine up to operating temp.

In summary, I am suggesting cold-engine oil changes may be better than hot oil engine changes because they are (1) Just as fast or faster, (2) more complete, (3) safer, and (4) more convenient (no warm-up time needed).

Go ahead. Tell me why I am wrong.

It is a recommendation, to standardize the oil change. If you live in the middle of the Sahara, and you want to change the oil in summer at 3pm ... you will not need to warm up the engine before doing the oil change. But if you live in the middle of the North Pole, and want to change the oil, in winter, at 6 am ... I assure you that it would be better to warm up the engine a little, even if you have a 5w20 ... Then, to avoid misunderstandings or interpretations by users ... it is better to standardize

 

[Top Ten]

No one needs to tell you that you're wrong; if you proposed the hypothesis, it's simple enough for you to test it and form your own conclusion. Do two oil changes; one with the engine warmed up to the correct temperature specified in the operator's manual, and one totally cold. You proposed four reasons why you believe a cold change is better, and three of them are simple to evaluate:

1) Just as fast or faster: That's simple enough to check. Set your standard for what constitutes "totally drained", and then time each oil change to see which takes longer.

2) More complete: If you define "complete" as the maximum amount of oil you can drain from the engine in an oil change, then that's simple enough; just measure the amount you drain from the engine during each change. The container with the most oil wins.

3) Safer: if "safer" means "less chance of being burned by a hot engine", then yes, I'd say changing the oil on a cold engine is safer.

4) More convenient: that's too subjective to define. If the task is convenient but inefficient, then the convenience is moot. It may be convenient to drain a cold engine, but if the amount of old oil you remove is less than what you remove from a hot engine, then the convenience is kind of pointless because you haven't removed as much of the old oil from the engine as possible, and that's the whole point of the exercise.

Your response is very direct and to the point. Thanks for that. Instead of saying "Tell me why I am wrong," I should have said "Tell me if there is something I am missing in my thought process; some obvious reason why a hot engine oil change is always better than a cold engine oil change."

 

[Cycledude]

I suspect Top Ten’s idea might actually be very accurate ! But yes we have always sort of been taught your supposed to drain Oil while it’s hot. After reading what Top Ten said I’m starting to believe it really doesn’t make any significant difference weather the oil is hot or cold when drained.

my Goldwing holds 5 quarts of oil and when you drain it only 4 quarts come out, so 1 quart always remains in there, many folks believe that’s a bad thing but the bike currently has 553,000 miles and It still runs like new.

 

[Top Ten]

I suspect Top Ten’s idea might actually be very accurate ! But yes we have always sort of been taught your supposed to drain Oil while it’s hot. After reading what Top Ten said I’m starting to believe it really doesn’t make any significant difference weather the oil is hot or cold when drained.

my Goldwing holds 5 quarts of oil and when you drain it only 4 quarts come out, so 1 quart always remains in there, many folks believe that’s a bad thing but the bike currently has 553,000 miles and It still runs like new.

553,000 miles! Wow. I, too, have a Goldwing. A 2012. I've never measured the oil I get out, only what I put in, four quarts. I have a little over 35,000 miles on the Goldwing and four quarts has always brought it up to the right spot on the dip stick. I just checked the manual for the Goldwing. It doesn't mention capacity; just that if you do an oil and filter change to add 3.9 quarts.

 

[jrusell]

I've been changing oil in cars, trucks, motorcycles, lawn mowers, garden tillers, etc. for close to 50 years now. And I have always done it with a hot/warm engine. I did oil changes hot because the oil was thinner and would drain more completely, and any particles in the oil would be suspended and would come out with the old oil. But after reading up on oil viscosity, multi-grades oils, how multi-grade oils change viscosity with polymer additives, I have come up with a hypothesis.

Multi--grade motor oils, say 10W40 for example, have a viscosity of 10 at cold temperatures and 40 at operating temperatures. The polymer additives expand with heat and cause to oil to thicken at operating temperatures. I think the technical temps are 0 degrees F cold and 200 degrees F hot. Based on that information, the oil should actually be thinner cold than it is hot. Or at least flow just as well cold as hot. Right?

Making the assumption that cold oil is as thin as hot oil, what is wrong with doing oil changes cold? If the oil is thinner, it should drain out as fast or faster than out of a hot engine. With a cold engine, all of the oil is already in the crankcase or oil tank, where, with a hot engine, you still have oil in the upper reaches of the engine that need to drain down to the crankcase. As to suspended particles in the oil, with modern machining tolerances and good filters, there shouldn't be many particles in the oil. And how many of us have gotten hot oil on our hands, held hot parts, or been burned by touching a hot engine part? And a cold-engine oil can be done anytime; no need to ride first or bring the engine up to operating temp.

In summary, I am suggesting cold-engine oil changes may be better than hot oil engine changes because they are (1) Just as fast or faster, (2) more complete, (3) safer, and (4) more convenient (no warm-up time needed).

Go ahead. Tell me why I am wrong.

You are confusing a few things.
Multigrade oils are designed to get you the best of both worlds. Flow like a 10wt when cold for easier startups etc, and flow like a 40 wt when hot to provide better protection etc. But what you are missing is it flows like a 40 wt does at 100 degrees vs what 10 wt does at 100 degrees.
Here is a chart that better describes the concept using 15w-40 as an example, but 10W-40 or whatever is the same. Easy to get confused, but when have you ever had hot oil come out of your bike as slowly as cold oil going in? Never.

 

[magic]

I actually tried it once. It took FOREVER to drain the old oil. I'm sure when someone drops their vehicle off at a dealer or service center to have the oil changed the dealer doesn't drive it around to warm it up first. So, there are probably lots of cold oil changes going on.

 

[Cycledude]

553,000 miles! Wow. I, too, have a Goldwing. A 2012. I've never measured the oil I get out, only what I put in, four quarts. I have a little over 35,000 miles on the Goldwing and four quarts has always brought it up to the right spot on the dip stick. I just checked the manual for the Goldwing. It doesn't mention capacity; just that if you do an oil and filter change to add 3.9 quarts.

yes like I said earlier you can only drain out 4 quarts, to remove quart number 5 you would need to disassemble the engine. The service manual pretty much explains this.

 

[Jlq1969]

4.2 liters in assembly. 3.1 without filter change ... 3.4 with filter change. There will always be at least 800 cm3 of dirty oil inside the engine

 

[OldRider]

I'm never in a hurry so I like to pull the drain plug and let the oil drain for 24-48 hours. It will drip for hours.

 

[Top Ten]

yes like I said earlier you can only drain out 4 quarts, to remove quart number 5 you would need to disassemble the engine. The service manual pretty much explains this.

Yep. I can see where you edited your first response to clarify your answer.

 

[Sierra1]

Hmmmm. . . . I've always changed it hot. . . . 'cuz that's how my dad taught me. But, while I was reading these posts. . . . it hit me. The brand new oil coming out of the jug is not hot. And, it seems to empty out of the jug just fine. I usually leave it drain into the motor for about 15 minutes, to get every drop. And, after the jug is drained, it's completely empty. So, why should our motor be any different? Flow wise anyway. Might call for an experiment.

 

[Skytower]

So, why should our motor be any different?

Running the engine suspends more particles in the oil. Draining it hot flushes more particles out. It also takes less time to drain, especially when it's cold outside.
Have you ever tried to drain a differential's gear oil when it's cold? Good luck pulling that off with a cold diff!

 

[Tenman]

Just drained my differential. 14K miles still looked new.

 

[Sierra1]

Maaaan, this is Texas. If I had to wait for a cold day to change my fluid. . . . And, although similar, motor oil, and diff oil are way different. Especially when it it's cold.

 

[Skytower]

Maaaan, this is Texas. If I had to wait for a cold day to change my fluid. . . . And, although similar, motor oil, and diff oil are way different. Especially when it it's cold.

There are differences in those oils, but you missed my point. The flow differences between hot and cold was what I was using as an example...
Don't take my word for it. ​

Filter the oil you drain, then show us the results. You'll learn, and confirm, what some of us are teaching you.

 

[Sierra1]

Running the engine suspends more particles in the oil. Draining it hot flushes more particles out. It also takes less time to drain, especially when it's cold outside.
Have you ever tried to drain a differential's gear oil when it's cold? Good luck pulling that off with a cold diff!

Draining "hot" will not "flush" anything. It might flow quicker, but not life changingly quicker. You will never get all of the oil, or contaminants, out of the entire engine. I depend more on my filter to get those nasty little particles, more than the oil dragging them out.

There are differences in those oils, but you missed my point. The flow differences between hot and cold was what I was using as an example...
Don't take my word for it.
Filter the oil you drain, then show us the results. You'll learn, and confirm, what some of us are teaching you.

And, my point was that the oil that I put into the motor, is not warm, yet it flows very well. In addition the bottle empties quite quickly, and completely. As I said, I've always drained hot/warm. But, Top Ten's questions got me to thinking. . . .