When does moisture get into the oil?

Patman

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This is something I've always wondered. Does moisture get into the oil right after you have shut the engine down and the oil is cooling, or does it get created right after you start the engine from a cold start? One of the reasons I am curious, is because I'm trying to figure out if I have properly stored my cars in the past for the winter. I would usually change the oil right before storage, but I would drive the car and fully warm it up before putting it away. Should I have simply changed the oil and poured in the new stuff and not started the engine?
 
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I always figure if you have water dripping from the exhaust, you probably have it in your oil. If it is hot enough too dry out your exhaust, you are ok.
 
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The water is a byproduct of the combustion. The O2 and HxCx(gasoline) combine to form CO2(carbon dioxide) and H2O(water) and small amounts of other, unwanted, compounds. So, the majority of the exhaust coming out of the tailpipe is nitrogen(from the air), carbon dioxide and steam.
 
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Another way it can happen is by condensation overnight. If there's condensation on the outside of the car, there's condensation inside the engine too. The only time water becomes a problem is if you make a lot of short trips and it never burns off. As long as you get the car out and get the oil hot (over 100C) occassionally, it will boil it all off.
 
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Remember, the engine is constantly having blowby into the crankcase. A good portion of this is steam. If the interior of the engine is cool enough(such as upon startup), it will condense. As soon as the crankcase is warm enough, it begins boiling the water out, where it is evacuated via the PCV system. [ June 25, 2002, 01:44 PM: Message edited by: VaderSS ]
 

Patman

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quote:
Originally posted by VaderSS: The water is a byproduct of the combustion.
So what you're saying is that most of the moisture gets into the oil right after you first start up the car then? I always drive my cars long enough to burn off the moisture in it, I was just curious as to whether or not the moisture would have been sitting in my oil all winter long, or if it was mostly created on that first cold start.
 
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That would be correct. The majority of the condensate happens in the first few minutes after startup. This is why short trips will load an engine up with water.
 

Patman

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I had figured that was the way it worked, and have always advised my friends against starting their cars in the wintertime during the storage period. Some of them would go out once a week and start the car and idle it for 10-15min. I can only imagine the condition of their oil after that 3-4 month storage period. Or the inside of the engine from all the moisture for that matter.
 

Patman

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I've got another question on this topic. I wonder if my weekend habits are causing moisture to get into my oil, causing minor corrosion overnight. Here is the situation. Because we have a single car driveway, and we use my wife's car on the weekends, after I do my morning errands in my own car, I park it in visitor's parking here at our townhouse complex. Later on once we're done using her car, and put it back in the garage, I then move my Firebird back into the driveway. By this time though, the engine is stone cold from sitting 8 hours or more. I run the engine for less than a minute and the car is driven only a few hundred feet. Do you guys think this causes any serious amount of moisture to accumulate in my oil? I worry since then the car sits overnight after having been run such a short time. I don't usually have the opportunity to drive the car longer when I do this, otherwise I would. The rest of the week this doesn't happen, so it's only on Saturday night and Sunday night. I've always wondered if this habit of mine is one of the reasons my iron levels are usually a bit higher.
 

Jay

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VaderSS is right about water being a byproduct of combustion. Each gallon of gas burned produces about a gallon of water. So engines operate in a very humid environment. I was trying to measure kinematic viscosity at 100*C by heating oil in my oven. I was having quite a bit of trouble doing it and at one point set the oils outside to cool a bit, then I tried heating them again. I was amazed at how much moisture they had absorbed. My oven was totally steamed when I reheated them. Your practice of starting the cold Firebird to move the car just a few hundred feet is hard on the car. Anything you can do to avoid that cold start will greatly reduce wear.
 
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quote:
Originally posted by Patman: I had figured that was the way it worked, and have always advised my friends against starting their cars in the wintertime during the storage period. Some of them would go out once a week and start the car and idle it for 10-15min. I can only imagine the condition of their oil after that 3-4 month storage period. Or the inside of the engine from all the moisture for that matter.
On the other hand, an engine that isn't run at all for such a long time (4-5 months) will rust inside from lack of lubrication and condensation build up. This is from Blackstone's FAQ:
quote:
I haven't even used this engine in six months. Why is wear high? The old adage is still true: use it or lose it. Inactive engines tend to build up moisture on the inside. That moisture causes corrosion, and when the engine is started up, all that corrosion is scraped off into the oil. We suggest frequent oil changes after a period of engine inactivity, to reduce the abrasiveness of the oil
What I would do is drive the car at least every 15 days or so to keep the above from happening. But even if driving isn't possible, I think even idleing for 20 min or so would be a better option that not starting the vehicle at all. Rick
 
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Patman; Speaking of your UOA, in my humble opinion, you tend to be a bit unrealistic. All engines will wear, no matter what oil or additive you run. You often compare your car with your wife's Civic, and you simply CAN NOT do that. They are made of different materials and/or made with different techniques, your F-Bod is more than twice the size of the Civic's 1.8 and carries less oil proportionally. I posted THIS on your last UOA thread and nobody seemed to care and/or nobody wanted to prove me wrong.Where are the experts at? Maybe I was right after all. Keep in mind that this is not an insult or attack in any way/shape/form. Rick
 

Patman

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Rick, I don't really try to compare my wife's results to mine anymore, I do realize that with such a large engine with obviously more metal, it's going to show higher ppm. I agree that the less cold starts like this the better, but I'm wondering if there is much moisture created if the engine is run for less than a minute. Perhaps the moisture doesn't start being created until the engine has a little bit more heat in it? Maybe more moisture is created once the coolant temps hit 100F? Tonight when we arrived back home from visiting my parents for Sunday dinner, and it was time to move my Firebird back into the driveway, I took it out for a ten minute drive. The oil didn't get completely up to temperature, but who knows, maybe it was the better thing to do? Perhaps I'll never know for sure. [I dont know]
 
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Pat; If this site has a negative side effect, is that it makes "us" worry a bit too much about oils. I'm sure the moisture amount when you do the above is negligible; it would definitely burn off the next day when you drive you car to work. Rick
 

Ron

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Santa Fe,N.M.
Hi,if exhaust tailpipe water is any measure of what's in the engine & oil pan,I better drain the water out quick! My Ford Van('99 4.2L six) discharges lots of water hot or cold,or just sitting looking stupid!Actually, after hours at highway speed, it dribbles(guess i do too). After 5K miles on D-1,I'm parking the van(monthly drive around)until the end of the year. We'll see what the UOA shows. Maybe, 1/2 Oil & 1/2 Water,or worser! [I dont know]
 
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PA
quote:
it can happen is by condensation overnight. If there's condensation on the outside of the car, there's condensation inside the engine too.
I believe this is where the majority crankcase water comes from. Water + old oil = yuck! This is another reson I believe in twice yearly changes, *after* the wide temp swings that cause condensation inside the block. Drain that contaminated oil out in May and November.
 
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NM
quote:
Originally posted by Ron: Hi,if exhaust tailpipe water is any measure of what's in the engine & oil pan,I better drain the water out quick! My Ford Van('99 4.2L six) discharges lots of water hot or cold,or just sitting looking stupid!Actually, after hours at highway speed, it dribbles(guess i do too). After 5K miles on D-1,I'm parking the van(monthly drive around)until the end of the year. We'll see what the UOA shows. Maybe, 1/2 Oil & 1/2 Water,or worser! [I dont know]
Ron; Don't know if you are jokin or not! I have noticed many vehicles have water dripping from the exhaust pipe(s), ESPECIALLY on Ford vehicles, to include Lincoln and Mercury. I don't know what is it with the Fords, but they do it more than any other vehicle I know. Anyway, NOT all of the moisture makes it to the oil pan; ONLY the blowby, which is a bit of combustion gases making it past the rings with a very small amount of water vapor. Like I said guys, don't stress about this too much! My belief is that the real killer is storing a vehicle and not starting it at all....the water would never get burned off. Rick
 
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This discussion reminds me that I had mulled over the theory that using a block heater would be good up north here because the oil would have a shorter time before it reached "boil off" temperature and the warm block would probably stop some condensation. Never did anything about it though, the mobil one comes up so fast I lost my motivation. [I dont know]
 
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I route my PCV gasses through a condensation can before it is ingested into the intake on my '97 SHO. This was done to try and reduce the amount of blow-by gasses that condenses on the Intake Runner Manifold butterflies and secondary intake valves. When the gasses condense on these internal engine components, heat soak will drive off the more volatile components and turn it into carbon. Anyway, what I have found is that if I seal off the intake side of the PCV system, which is the hose that goes from the pre-throttle body intake to the valve covers, I reduce the volume of condensate I collect from the can in half. When I let this condensate sit it will settle out around half and half as water and oil. But the quantity of water is doubled if the PCV is allowed to draw in ambient air. By sealing the intake side of the PCV system on the SHO motor I can maintain about a 5-7" Hg vacuum on the crankcase which seals the rings better and reduces the blow-by too.
 
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