interesting conversation about draining oil

[the Ferret]

Since I woke up it's been pouring rain. Might be the first day this month I won't get to ride. So my other bike needs it's oil and filter changed, might as well do that today. Was talking to one of my good riding buddies this morning about what he was doing instead of riding today, and he was basically doing the same to his bike on this rainy day.

He says "are you going to warm up the bike before draining the oil?"

I said "I always do, don't you?"

He says "nope, the last time I rode it the oil was warm and when I parked it, all the warm oil drained down into the sump".

I said "yea?" questioningly, like, where are you going with this?

He says "well, if you start it again you are just going to push dirty oil from the sump up into the top of the motor again, where it has to drain back down, so you can drain it from the sump".

I said "That's true, but won't it drain faster from the sump when it's warm?"

He says "Ever open a bottle of oil that's been sitting in your garage for a few weeks?"

I said "yea?" again wondering where he's going with this

He says "did you have any trouble pouring it out of the bottle?"

Hmm now he's got me pondering. Since I was a little kid I was told to heat up oil before draining it, but he's got me thinking now. All the dirty oil did drain down when I last came in from riding and parked the bike I have to assume. Do I really want to push that dirty oil back up into the top of my engine now?

Oil might not get changed until tomorrow. I have to work this out in my head. He may have a point.

What do you think?

 

[12cb96vfr_imp]

I do it cold personally.

 

[Paulb_imp]

Maybe the rule of warming the engine goes back to times when oil was really thick and not as we know it today. I bought a Vintage speedway bike earlier this year and the engine is a 1947 J.A.P 500cc single which is designed to run on Castrol R (smells great). When I disconnected the pipe from the oil tank to the engine to drain the tank nothing came out for ages and finally it flowed as a tiny line, almost breaking into single drips. I checked with Castrol to find a more modern oil to use but they said this engine was designed to run on Castrol R and warned me to warm the engine quickly to heat and thin the oil otherwise the head would not get lubricated properly. So, I think your friend is probably correct and modern oils do not require old fashioned drainage rules.

 

[ss2wheels_imp]

I think like every other oil thread it makes no difference one way or another, just change it when you are supposed to and it will be good to go

 

[coach50_imp]

I change the oil cold on all my bikes & cars. As long as one waits a day or 2, all the oil that's going to drain down will have by then. Of course, as posted above the "cold" oil viscosity ratings for vehicles are lower than in back in the day...

 

[jmc1100_imp]

I doubt a dealership would pay the time to warm an engine before an oil change. Sound advice...

 

[silverbub_imp]

If you are using 10W30...then maybe the question is whether you want an ambient(cool) drain at ~10 weight... or a warm to hot(operating temp) at ~30 weight?... To me... flow rate would be of some consideration so as to flush out the "gunk" residing in the sump pan...I go with a "warm-hot" drain after a nice local ride... have lunch(whatever)...then drain & let drip for some time...I have gotten about an extra 8-10 oz of accumulated dripping by leaving off drain plug for a reasonable time(an hour or so) after the initial drain flow...I presume you are talking about your ST1300 here & so am I...

 

[Tim_in_AZ_imp]

Not so much the flow rate of the warmer oil, but any 'gunk' that has settled has a chance to be put back into suspension so it is flushed out.

 

[the Ferret]

I just thought it interesting. I had never heard of anyone changing oil cold, had not been taught that way and never considered any other way than changing it warm. Another wives tale? Or is there science behind it?

The part about reintroducing dirty oil (and it's contaminates) back into the top end is what really got me to thinking.

Tim makes a good point too, putting gunk into suspension so it can come out, but how much of that gunk will get trapped in the head/oil lines/and on our bike (oil cooler) if you heat it up and circulate it through the system?

Unlike a typical oil thread, this conversation is relevant no matter the brand or weight.

Also had not heard of anyone changing gears without the clutch though lol

I must live in a cave lol

 

[silverbub_imp]

Not so much the flow rate of the warmer oil, but any 'gunk' that has settled has a chance to be put back into suspension so it is flushed out.

Yes, that too, certainly!... Thanks for clarification... flow rate AND SUSPENSION OF 'gunk' GOOD!:hello:

 

[coach50_imp]

Not so much the flow rate of the warmer oil, but any 'gunk' that has settled has a chance to be put back into suspension so it is flushed out.

I'm thinking most if not all of gunk should be captured by the filter, unless its pieces of really small gunk that passes through the filter. In which case I'd imagine the pieces would be brought to the sump by the returning oil anyway,to be drained out with the oil. Just MHO.

For me, the bottom line either approach is less important that following the recommended maintenance intervals.

 

[Motogeezer1949_imp]

I love these kinds of threads

 

[the Ferret]

For me this thread is a learning experience. Being an old dog and all, I tend to think I'm pretty sure how thngs work, how things should be done, etc because I have a lot of years of experience, even worked in the industry for nearly 2 decades, yet turns out maybe I can learn something after all.

 

[redbirds_imp]

A learning experience indeed. Changing the oil cold makes sense to me. Modern multi-grade oils seem to show little if any difference in flow whether hot or cold.

 

[quietguy_imp]

I would lean towards the oil being circulated, drained hot/warm, then allow the system time to drain fully. I also concur with the premise the oil filter [should] collect a great deal of the dirt/debris.

The filter contains much of the "solids", the dirty, contaminated fluid is removed and replaced with clean, along with a new filter.

But a brain surgeon I'm not...

 

[Motogeezer1949_imp]

The theory of changing while warm supposes that any sediments will be put into suspension and easily evacuated when drained. Conversely, draining when cold theorizes all scrud has had time to work it's way down into the crankcase and assumes it too will drain when the plug is pulled. In my experience, there will be no dirt, no debris, no particulate, no scrud to be found in any well maintained modern motorcycle engine. Why? Because of the oil filter.
Pull an oil pan or two and check for yourself. Or, if you're not up to going to that much effort, next oil change, cut open your oil filter and post up some pics of your findings. That said, if one is still concerned about sediment being left in the pan, after draining, run about a half quart of clean oil through and let it drain thoroughly before buttoning the pan back up. The theory being, a little extra rinse to clean out the pan can't hurt

 

[Jim21680_imp]

Given a choice, I'll do it cold....but I won't think twice about doing it hot or warm either. Remember, it's not worth over-thinking this!

 

[kmoney_imp]

Not so much the flow rate of the warmer oil, but any 'gunk' that has settled has a chance to be put back into suspension so it is flushed out.

This is the reasoning I've always been told as well. I've always somewhat blindly followed it and never questioned it.

 

[immgunn_imp]

Undeniable fact of life #39, hot oil drains faster than cold oil. So maybe the question should be, "how much is your time worth?"

 

[flynrider]

I usually drain it when hot. I follow the theory that the dispersant additives in the oil (used to suspend tiny impurities in the oil and prevent sludge buildup) are doing their job when the oil is near operating temperature. The oil is also noticeably thinner when hot and definitely drains faster, and it may be my imagination, but I feel that the thinner oil drains more completely.

When it comes down to it, I'm not fanatical about doing it one way or another, but when it's convenient I do it hot.

Hot or cold, I usually let it drain for a half hour or more.

As an aside, my air-cooled airplane engine is supposed to be run to operating temp before an oil change to allow the dispersants to do their thing.