OK to start it's a 2004 freestar SES 3.9 it has about 141,000 miles on it. My wife said she could hear a knocking sound so I drove it and sure enough. Only while going up a hill or pulling out slow. Changed plugs and wires. A few of the plugs were fouled badly. Got to looking and the PCV valve is letting oil past it and allowing oil to get into the intake. So on down to the plugs. Replaced PCV valve because thought it might be bad and still letting oil thru. Runs excellent so are the rings bad or something else? Replace the EGR valve about 2 years ago because of a broken part on it. Any suggestions?

 

I did a little research and came up with two possible reasons for this:

1. compression rings may be going bad.

2. EGR may cause some pumping action.

How often do you change the oil and what oil do you use?
Was that EGR repair done correctly? Did you replace the gasket?

 

OK...Here's where everyone will have their opinion...

But...Here's what I have just done...

I have no engine noises, but do have more oil blow-by in the PCV valve then years/mileage before.

I have run AMSOIL 100% Synth 10W-30 in my Freestar since it had 5,000 miles on it. In the past couple of years, it's been munching about 1.5 quarts of oil between its yearly oil change.

On my road trip last September to Arizona and back, it used a quart of oil there and one quart back.

The start trip mileage to Arizona was about 121,000 miles and the return trip mileage from Arizona was about 126,000 miles.

Like I mentioned, its had nothing but AMSOIL full synth 10W-30 in the engine.

At 133,000 miles, I drained out the AMSOIL and added 4 quarts of Wal-Marts Supertech 10W-30 synth oil and 1 quart of Marvel Mystery oil and ran it for 2,500 miles, then drained it. Then I did another fill of the same and fixing to leave to Arizona with 135,700 miles on the van.

I suspect that even thought I have run AMSOIL, just like anything else, I may have a build up of crud around the oil and compression rings. Thus, I'm doing a MMO cleaning of my engine to see how it does. I've used MMO years before I started using AMSOIL with no issues, so I'm giving it a shot to see what it does. If there's no change, then it's just plain ole' engine wear. I'll be gone for 2 weeks, but will update my oil usage / results when I return.

Remember...This is just my senario/case

 

I change the oil about every 3,000-3,500 miles. Use a ford filter. I've used Wal-mart brand, Advance auto brand. Even used Lucas oil treatment and still does it. I have put about a 1/4 of a can of seafoam in a couple of times to clean engine out. I have ran that a few hundred miles before oil change. All this started about a year ago, have had the van for over 4 years now. I changed the EGR myself, I can't remember if I changed the EGR gasket with a new one or what. No metal in the pan as far as I know, and no metal on the oil plug.

 

Do you think I need to take out the EGR and clean/check it. No codes.

 

Just throwing a couple of other things out there...

Well, being that the EGR valve is only 2 years old, I would suspect it as being OK. It's just a vacuum operated valve. Mine has never seen a wrench.

Oil in the PCV valve is caused by combustion blow-by. You could check the intake hose for the PCV system and make sure it's OK. The hose runs from just in front of the MAF assembly to the other valve cover. You will need to remove the upper/lower cowl to access the other valve cover.

Also, is it a knocking or a pinging that you hear?

If it's a deep, low tone knock, it could be rod bearings from wear. Have you tried upping the fuel octane to see if it goes away? If it does, then it's pinging and usually associated with carbon buildup in the combustion chamber. Does it knock when cold, warm or both?

 

According to Motor Oil 101 - Bob is the Oil Guy we all seem to use too thick an oil. I believe we should use 5W-20. The Lucas Oil stabilizer is even thicker. I will switch to the 5W-20 with my next change.

If you use long distance oils you still need to periodically change the filter.

Use Common Sense in my opinion is on the right track with internally cleaning the engine.
One thing that has made my engines run really nice is a catalytic converter cleaning with lacquer thinner (NOT PAINT THINNER!): It cleans more than the cat. the solvent may even clean the rings when it gets blown by them.

When done with the cleaning you may also try "Restore" oil additive. It fills in scratches in the cylinder walls and thus reduces blow-buy.

 

If you are not sure that you used a new gasket then replace the gasket. It is cheap enough to eliminate this possibility.

 

If that car is getting through 4 and a bit litres of oil in 250 miles there's something seriously wrong with it, and I'd be taking it to a different garage if they cannot find the source of that size of leak/consumption.
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2013 MERCEDES BENZ SL-CLASS

 

In principle you are right, rocky. However i can't find where the OP stated that level of oil consumption.