What was the goop?

[wbwanzer]

A few weeks ago I changed the oil in my mother-in-law's '05 Volvo S40, at least I think it was an S40. Small car with 5 cylinders. Lest anyone think I'm a complete moron, I knew the model at the time of OC, just not sure of it right now. Anyway, the underside of the oil cap had some goop in it that kind of looked like butterscotch pudding (very light tan color) and was almost the same consistency.
I cleaned the goop out and at first thought it was from an overfill of oil. When I drained the old oil it darn near overflowed my drain pan there was so much oil. But then when I filled it, it took seven qts instead of four or five. So them I'm thinking the goop was not a result of overfill. Now I'm thinking it's from condensation. This '05 is seldom driven (7500 total miles) and when she does drive it's always very short distances.
Am I correct in thinking that the soft goop is a result of condensation? If not, what do you think it's from?
I don't know when the last oil change was before the one I did, but I do know that it had been changed at least once before my change.

Thanks for your input.

 

[MGregoir]

Yes, it is condensation.

 

[Junior]

Yep, the result of short trips in cold weather.

 

[rewote500]

Could you go into a little detail about why short trips in cold weather cause condensation?

 

[demarpaint]

In simple terms, the engine never gets the oil hot enough to boil off the moisture that forms from short trips. The moisture forms that milky substance when it mixes with the oil. The engine needs to be driven for at least 20 minutes or longer to get the oil hot enough to burn off the moisture.

 

[Junior]

Originally Posted By: rewote500
Could you go into a little detail about why short trips in cold weather cause condensation?


Without getting into the chemical equation, when hydrocarbons are burned the reaction produces large amounts of Carbon Dioxide and Water Vapor along with other gasses. The exhaust and water vapor is at 300-1000+ F depending on engine load. Most is expelled out the exhaust. But some passes by the compression and oil control rings around the pistons and in into the crankcase. This is commonly called blow-by.

The blow by makes it's way into the valve covers through the oil drain ports that allow lubricating oil to drain from the top of the engine heads. During cold weather after a cold start the entire engine including the valve covers are cold. When this warm blow-by (mostly CO2 and Water Vapor) encounters the cold surface it is cooled to it's saturation point, condenses and collects on the inside of the cold engine. If the engine is never allowed to fully warm up and heat soak, this water collects over time and combines with oil vapor, unburned hydrocarbons etc. to form the visible whitish-brown silme on the oil fill cap.

In even simpler terms, think of the cold engine as an ice cold beverage. The exhaust is the air on a hot humid day. Condensation forms on the outside of the glass. Same thing happens on the inside of a cold engine.

 

[Johnny]

I might add to demarpaint's comment about being driven for 20 minutes. That's not 20 minutes around town, that will just product more condensation. Take it out on the highway for 20-30 minutes at highway speed. That will warm things up enough to displace the condensation. And even after that you still might have some of that white substance in the oil cap, but it will be gone from the engine.

 

[Ursae_Majoris]

Newbie post here. If you have a plastic oil filler tube, the "goop" will be more evident. My 05 Tacoma has one, and temperature difference between a hot aluminum engine and a warm plastic tube exacerbates the problem.

It is one of the top 10 questions on Tacoma boards.

 

[ARB1977]

Originally Posted By: Ursae_Majoris
Newbie post here. If you have a plastic oil filler tube, the "goop" will be more evident. My 05 Tacoma has one, and temperature difference between a hot aluminum engine and a warm plastic tube exacerbates the problem.

It is one of the top 10 questions on Tacoma boards.

Im sure glad my 2002 Tacoma doesnt have that issue...Welcome to the board.

 

[Junior]

It's not a design issue. It is a function of operating conditions. Take your Tocoma where is is cold, do some short trips and you will see the "goop" too.

 

[demarpaint]

I guess I'm pretty lucky, the only "goop" I've seen in one of my engines is the snow blower engine if I don't run it long enough.

 

[wbwanzer]

Thanks guys. You've confirmed what I thought.