bmwm750

If you're going through oil, you've got bigger problems at work here.

If you have the time to wait, I'd highly suggest an oil analysis to see what's really going on.

snapdragon

It looks a bit dark, but could it be an oil/water emulsion (mayonnaise?)

mishar

This looks like result of mixing oils of a different origin. Mineral+vegetable would result in this kind of sludge in no time. Everything else would take more time.

2fast2c

I'm having other symptoms and maybe they are related.

btw, I'm losing any oils now. Level is pretty consistent.

Here are some facts:

I've been adding some coolants every 10 days or so for a while now. I didn't really find any leak on the floor. This is before low engine oil level light issue.

I guess there is a leak somewhere but I can't figure it out, I can't get underneath the car so I don't know where and even if it is, it must be small.

And when I did an oil change, that's when I found out about oil sludge. By the way, after oil change, low engine light has not come back yet. But I got low coolant level today. Mechanic topped it off when he did an oil change which is about 2 weeks ago.

Any thoughts??

bmwm750

Yup. You're getting engine oil/ coolant intermix. Usually this manifests itself as a coffee colored frothy milkshake in the oil, with small oily residues in the coolant, but it can certainly cause sludge as well.

Could be head gasket related, or oil cooler related.

I would not drive the car until you sort this out, as coolant compromised oil has significantly less lubricity than clean engine oil and can wipe a bearing in no time.

MP4.2+6.0

+1 What he said.

JohnnyJ A6Q

Do Not run that engine until you check the oil for antifreeze !!!
Get a black light and look at the old filter if you still have it, or at the oil you now have in the engine.

Do a leak down test to see where fluid is going, or a compression test, or put air into each cylinder and see if you get bubbles in the coolant tank.

Did you have bubbles in the coolant tank while it was running ?

There are so many ways to test this, BUT PLEASE DO NOT RUN THE ENGINE UNTIL YOU KNOW WHAT'S WRONG, or you will be very displeased when your engine is seized up.....

"Antifreeze
Manufacturers purposely include fluorescent additives in antifreeze fluid so that black lights can be used to find antifreeze splashes to help investigators reconstruct automobile accident scenes."

2fast2c

Looks like I'm in a big trouble. Damn it.

Ok, I get the picture. So in which order should I do these tests?


Is it worth fixing it or should I get rid of it. I really love the car however it's 07 with 105k miles on it. Just put 2 brand new tires and all 4 rotors and pads. front suspension needs to be replaced. Still owe about 15k....and still drives nice though......

MP4.2+6.0

In the "old" days, coolant in the oil was virtually always a big internal engine repair bill. On the "lighter" end of that, a bad head gasket. On the scarier end, potentially internal cracks in either the head or the block. But now with increased use of coolers from the oil to the cooling system (as well as the tranny and diffs in higher load applications like S8 and W12), it also means the cross contamination can be with solely external engine parts. Still a pain and $ to repair and flush engine and such, but maybe somewhat less work than the head gasket scenarios, and a lot less work, $ and possible downtime than internally cracked motor components.

There is a low incidence of posts I've seen over many years on anything internal engine, so I would put more weight toward things like the oil cooler scenario. You need the experienced diagnostic check though.

bmwm750

On the German cars which use coolant/ fluid (oil/ transmission/ gearbox) heat exchangers, it's not all that uncommon for them to become compromised and cause intermix. My hunch would be that this is where your problem is. Sadly, unlike on a lot of the Porsches, in your case, it's a decent size PITA to get in there and swap the unit out.

I'd start with an oil analysis to confirm that this is what's going on, and then, assuming that it is, start searching for the cause of the intermix.