I added some oil this afternoon for the first time in several months (second time since I got the car in July). When I opened the cap, there was a creamy yellow goo underneath. It look like it could have been thickened oil. I have never seen anything like this, but then I got to thinking that the oil isn't poured directly into the engine, but rather into a hose that leads to the engine. It didn't look like there was more down the hose (as best as I could see). Is this normal, or should I be concerned? FYI, the car is a 2007 C4, bought new by me and the only oil added (other that by the factory) has been Mobil 1 0W40.

 

I believe it's an artifact of 'normal' condensation. I heard and read of this before.

 

When you see this it is an indication that you are not driving the car enough, and that you are probably in a relatively high humidity area. Short drives in which you aren't getting the engine temperature up high enough to cook off that moisture is what is doing that. It's not a big deal, but something to understand.

 

Thanks. Makes sense, as I basically drive the car to work (7 miles) and the golf club (6 miles). Also, We've had a warm spell here in CT (50s) and a lot of rain yesterday.

 

I am not sure that this is connected to how much one drives their car. I have had the same experience with my 07 C4. I've put 21K on the car since March. It seems to be related to humidity and temperature, clearing-up with warmer weather.

 

I had the same thing happen prior to full summer driving. That yellow/tan film inside the oil fill tube. It's normal from what I've been told by Porsche and by other owners.

Once the weather warms up, and you drive it more often, it will be gone. It took me some time before it was fully gone.

Once really warm weather came around, and I drove it more often and longer, the "goo" was gone.

Don't sweat it, just drive and enjoy, by late spring and early summer it'll be gone.

Deanski

 

Chances are, if the sludge is appearing in your oil fill tube, it is accumulating in other areas if your engine. You MUST bring your engine to maximum temperature for longer periods of time if you want to redeuce the sludge risk. There is no other way of eliminating it short of eliminating all humidity the car is exposed to. This also means you have substantial moisture in your cylinders at startup which is the leading cause of engine wear.

 

I don't know how useful this suggestion is, but take it for what it's worth:

I fly a Beechcraft Baron aircraft with two large-bore engines. One trick we use to eliminate moisture in the oil is to not only run the engines up to normal operating temperature for prolong periods of time (i.e. a 4.5hr flight from MI to TX), but also open the oil filler caps as we are putting the aircraft away to permit moisture/steam to evaporate. You can actually see it come out at first and after 20 minutes or so, the process has stopped and we recap it.

Such a technique might be appropriate for some here.

Just a thought.

 

Just came across this issue myself... Took the car to Vegas for the week (900 miles roundtrip) and lost about a quart of oil. With one month left on my CPO warranty, I was debating taking the car in for a look....

Glad to hear it is "normal". Even though I live in a very dry climate, it has been unusually humid of late.

-B

 

Interesting technique... may have to try this is I get the yellow gunk in my filler cap.

I put about 5K miles per year on my C2S and drive it a few times every week and make a point to hit the 5-6k RPM range to warm up the engine. I also installed the 3rd radiator which has cooled down the engine oil temp by 15degF... so far no gunk since I installed it over 6 months ago.

 

Interesting. 2007 C2S with 60,000 miles & never a trace of mayo in the oil filler cap. Probably due to (1) always driven 40+ miles each time out and (2) living in a dry southern cal climate.

 

no.

1. Its not sludge. Its an emulsification of the oil and water.

2. Its on the very top of the engine on a tube that extends quite a bit from the engine. It therefore does not get as hot as the cylinders, heads, etc., but yet the condensation ends up there because its the highest point.


its fine

 

I have this issue with my wife's 2000 CLK Mercedes. She has only 20000 miles in 12 years.
Short drives in cold weather. I change the oil based on time and not mileage. I also try to run the **** out of it every once and a while.

 

Yes I agree with this. I have always experienced this stuff in my oil cap even driving 15,000 miles per year. The moisture condenses in that tube. Just about every other engine has the oil filler right into the engine but the 911 filler is far away from the engine. The water and oil vapor rises up into that tube and condenses there. Perfectly natural event.

 

Thanks guys for the additional posts...

I live at altitude in a "high desert" climate (7500 feet), and have been driving the car as my daily-driver for almost two years. This is first time that I have seen the "goo", but then again it has been unusually moist (92 percent humidity) the last few weeks. Our usual moisture/air content is in the 15-35% range...