My 2008 ML350 been using about 1 qt of oil every 1000 to 1500 miles. Have 200k miles on it and replaced oil air separator about a year ago due to leak.
I was wondering if replacing this partial load oil separator could reduce oil consumption. Isn't this same as PVC valve?
Appreciate if anybody has information on this.

 

I'm not seeing the connection. Oil consumption is through rings or valve guides, primarily. Right?

PCV oil consumption should be an order of magnitude less than the other two consumption paths. Unless a gross malfunction is at work. Am I seeing this correctly?

Do you have a CEL on? Can you read codes, ideally with Xentry/DAS?

 

I know that engine with 200k miles on it will consume or burn some oil, and since this being original part maybe it might contribute to the oil consumption if it is clogged or doesn't function correctly.
Don't have any CEL and I used icarsoft. Putting oil in every so often just annoys me, seems like I've replaced whole oil by the time oil change is due.
I don't have any active oil leak on the garage floor.

 

Is this a diesel or gasoline engine? Are there any modifications on the powertrain?

What does the exhaust smell like? Do you change your own oil? What does the oil look and smell like? Same question for the coolant. Oil is going somewhere, either it is getting burned and going out the tailpipe, or it is going into the coolant, or onto the garage floor.

For a car of that mileage, I would be inclined to throw parts at it for good measure. How long have you owned it? I have run several cars over 200k miles, and I knew them like the back of my hand. If I wasn't sure of something, I would throw a few new parts at it and keep going.

 

That's my thinking. The part doesn't cost that much so replace it and hope that it does something to help.
I've owned this car since 24k and I do everything except AC work. Replaced coolant pump about a month ago and coolant is OK, I change my own oil and it is nice and black every time and I changed tranny filter and oil about every 50k. There is no smoke from tail pipe(at least none that I could see), car does smell like burnt oil from time to time.

 

Gasoline or diesel engine?

If the car smells like burned oil some times, the car is burning oil. If the coolant and the engine oil look good, that suggests the oil is not escaping other than out the tailpipe.

Now to narrow it down between valve guides, rings vs something else.

Have you disassembled the intake components to see if sludge is built up? Particularly PCV or oil separator components? If they are bone dry, then oil is getting past the valve guides and rings. With over 200k miles, my head is thinking toward engine hard parts due to age.