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I changed my oil yesterday and came up with another reason to change it hot. I was taking a sample for oil analysis. You're supposed to heat it up and get the impurities evenly distributed throughout the oil, so as not to skew the results.
Rboe, the oil temp needs to get to about 170-180 degrees before the moisture in the crankcase will vaporize. I have the same issue in my plane in the winter (it's even colder at 10K ft.). I have a plate that blocks the plane's oil cooler in winter. I'd like to do the same with the CB, but as you pointed out, you really need a temp gauge to figure out when and how much to block it.
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I always drain hot, cold would take the fun out of possibly burning your hands
Getting the motor up to temp will get all the condensation to burn off and/or mix with the oil which will be drained. With the CB your never getting a clean change with the oil cooler, .8 qt will always remain.
The same amount of oil will remain on top whether its a cold or hot change, once it finds its level ( nooks and crannies) that's all that's going to return. So I say change it hot
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(12-21-2015, 11:20 AM)The ferret_imp Wrote: 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.
My perspective also! (at least I try to maintain this perspective!
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I've always changed it hot, only because it's folklore, but I think changing it cold makes sense too. Like most of you, frequent oil changes are probably more important than hot vs. cold. I've never suffered an engine failure in 40+ years, so it's probably moot anyway.
Before reinstalling the drain bolt, I usually chase out any remaining oil with a few ounces of new oil. Once I see new oil flow out, I figure the old stuff is completely out.
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Alright, 5-page oil thread, it's time for a theoretical experiment (since I don't think we could accurately do this in real life, as a forum).
....Unless someone here owns two bikes.....
Two CB1100's have been sitting on their center stands for hours. The oil level in their sight glass is dead-on even with the line.
One starts up, and gets up to temperature. The other stays off. One is hot, the other is at room temperature.
The oil in both bikes is allowed to drain into a catch pan for 30 minutes, along with the two identical filters.
Which catch pan weighs more - the hot one, or the cold one??
My bet is on the cold one.
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Now I know why we all overfilled our bikes the first time we did an oil change. We added the stated 4.1 qts of oil after draining it when it was hot. We didn't get it all out so we overfilled it. The next time some one changes it, maybe do it cold and let us know how much it took to refill. I'm going to do mine next weekend... maybe I'll try it that way if I can get past the mindset that it's supposed to be done warm.
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Bob; why do you think the cold oil would weigh more than the warm oil? After 30 minutes, unless it was really cold, but let's assume ambient temps are 72 degrees F. In which case the same amount of oil should drain out - mass would be the same.
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No thermodynamics talk needed, you just missed the point I'm trying to suggest here: I think you'll get more oil out of your bike by draining it cold, rather than hot. My theory is simply based on where the oil is when it's cold vs hot.
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Did anybody ever try that experiment -- draining hot and draining cold and seeing whether more oil came out one way than the other?
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I'm really interested, because I've always drained it warm. From the first service, I've added 4.1 quarts, and... the oil is always fully above the level of the site glass. So far, no consequences (if I've indeed over filled), but, perhaps I'm adding more and more total oil volume each time I drain (less than 4.1 quarts) and then add back 4.1 quarts of new oil. I think I'll try cold next time, and allow like 30 minutes to drain.
Has anyone experienced a problem of overfilling? Will the oil "foam"?
