Moisture in oil

[Patman]

I just had to move my car so that we could take my girlfriends car to do some errands and I’m curious about how much moisture is created by starting a stone cold engine and then shutting it off less than a minute later? In a situation like this where not much heat builds up, will there even be any significant moisture in the oil?

 

[Donald]

I would not worry about an occasional running of the engine for a minute or two then stopping. We all do it.

What you don't want to do is to start an car in storage every week but never run it to full operating temp.

 

[JunkdrawerDog]

For a one off event as you described, I doubt that it's very much. Back in the seventies, my old Chevy Nova would produce a milkshake ring of moisture around the inside of the oil filler cap from batting around campus and never getting warmed up. It would remain that way until warm weather and it's spring oil change arrived. I don't think you have much to worry about.

 

[Patman]

This isn’t something I usually do at all but it just had me curious about the actual amount of moisture that gets in there for such a short run time. My guess is very little, that the engine needs more warmth in it before any moisture gets produced

 

[MRC01]

As a general rule of thumb, the amount of water created in a typical gasoline engine is approximately equal to the amount of fuel burned. The water is created by combustion so most of it goes out the exhaust pipe, but some gets into the engine since the piston ring seals aren't perfect.

So if you burn a cup of fuel, it will create a cup of water (vapor), most of which exits the exhaust valve into the exhaust system, a very small amount of which will get past the rings into the oil.

PS: that's not the only way water gets into the oil. Much of it comes from condensation. When the engine is running the air inside is quite warm so it can hold a lot of moisture. When you shut it down, as it cools off the air can't hold that much moisture anymore so whatever moisture was in it condenses out into droplets that become water in your oil.

 

[spasm3]

I think you would have to know how much air volume is present in the engine. Area of the bore under the pistons, the volume of area between the oil pan and around the crank. Area of the combustion chambers. Take that volume and calculate moisture at several humidity percentages. Everytime you start the engine, you turn over that volume with fresh volume at whatever humidity level is present.

 

[Legs4Arms]

I would not worry about an occasional running of the engine for a minute or two then stopping. We all do it.

What you don't want to do is to start an car in storage every week but never run it to full operating temp.

Agreed.
I short trip one of my cars daily to pick up my wife from work and I have to frequently replace the over axle section of the exhaust that isn't stainless due to all moisture that accumulates and doesn't burn off. Just another negative side effect of short tripping along with how it affects oil.

 

[Donald]

Agreed.
I short trip one of my cars daily to pick up my wife from work and I have to frequently replace the over axle section of the exhaust that isn't stainless due to all moisture that accumulates and doesn't burn off. Just another negative side effect of short tripping along with how it affects oil.

I went to a muffler shop once and he had some leftover sections of SS pipe and did a SS exhaust for my Jeep GC on the cheap.

I have no idea what the total exhaust costs for my F250 PSD with DPF filter and DEF injector. My guess is thousands.