[NCporsche]

We have a MB with 200k miles. The oil light came on and checking the stick it was down a quart but the oil appeared normal.

Opening the fill I noticed yellow goop. What is going on?

[BeerBurner]

Looks like you might have some coolant in there. :(

BB.

[NCporsche]

That was my first thought and was hoping for a different problem.

[fpena944]

Or another source of water. I know in my 996 if it is subject to many short drives the oil filler cap gets this same sludge. But a long drive will kill it all.

Is this car subject to mostly short drives where it doesn't have an opportunity to warm up?

[BeerBurner]

Good point. I forgot about that.

BB.

[NCporsche]

Or another source of water. I know in my 996 if it is subject to many short drives the oil filler cap gets this same sludge. But a long drive will kill it all.

Is this car subject to mostly short drives where it doesn't have an opportunity to warm up?

Yes. Typically drive once a week about 8 miles each direction with a 4-5 hour stop in between. Just completed a 25 mile drive when the light came on. The oil in the dip stick did not appear milky.

I can pull the filter w/o an oil change so this will be next.

[Scott at Team Harco]

Or another source of water. I know in my 996 if it is subject to many short drives the oil filler cap gets this same sludge. But a long drive will kill it all.

Is this car subject to mostly short drives where it doesn't have an opportunity to warm up?

Yes. Typically drive once a week about 8 miles each direction with a 4-5 hour stop in between. Just completed a 25 mile drive when the light came on. The oil in the dip stick did not appear milky.

I can pull the filter w/o an oil change so this will be next.

Short trips and cool weather will produce condensation in the engine. Longer trips and getting the oil up to temperature, for a good period of time, will burn off the water.

I suggest a good long drive and then an oil change. Then you need to avoid short trips as much as possible.

Be sure to keep an eye on coolant level. Coolant in the oil is bad. You don't want intermix.

[NCporsche]

The MB has not recently been driven for an extended drive because we have other more efficient vehicles. There is an airport trip next weekend that will be a two hour drive. Guess we are taking the Benz.

[AKSteve]

Actually, it looks like you've somehow made an aioli (aka Mayonnaise).

[N_Jay]

I would do a flush and change, and then check it daily.
Could be condensation, or a head gasket, or an oil cooler seal (if like the later MBs), or even an oil cooler.

[NCporsche]

Damn J, thanks for narrowing it down.

[N_Jay]

Wish there was a magic answer, but that looks like more than just condensation.
Water does not lube well, but oil cooler seals are usually not difficult. (Fingers crossed)

[NCporsche]

Actually, it looks like you've somehow made an aioli (aka Mayonnaise).

Steve, thanks for the idea. Thread title changed.

[Scott at Team Harco]

Damn J, thanks for narrowing it down.

Start with the simple, most likely cause (short trips/condensation). At the same time, monitor your coolant level. This is not rocket surgery.