What do you think is going on here? - PeachParts Mercedes-Benz Forum

nelbur · #1 07-01-2016, 11:38 PM

We have a '97 E300D with 245,000 miles. This is a NA diesel. For the last three 7500 mile oil changes I have tried three different 5W40 synthetic oils and had them analyzed thinking I would see which had the lowest wear metals. I was surprised to find that my chromium was three to four times the normal level, while the iron was very normal.

Blackstone thinks the chromium comes from the rings, but I cant figure out how they are wearing without the iron being high as well. With the engine idling, there is little blow by coming from the open oil fill hole, and no strange noise. The engine sounds the same as when I bought it 50,000 miles ago from my neighbor. Mileage is good. At idle there is a bit of nailing on one cylinder which I have thought was probably an injector. I am not aware of any injector work on the car.

The car is in good shape with no rust. It is garaged and the wife loves it. I haven't told her about the chromium. Given it's age and mileage, if the engine went bad I would likely look for a junkyard engine rather than try to fix this one, but I would love opinions on what is happening to give the high chromium.

The oils used were; Delo 400 LE, changed out recently; Mobile 1 TDT, on the previous change; and Rotella T6, on the earliest change. The iron was 26 ppm; 22; and 26 respectively. The chromium was 13 ppm; 11; and 7. Seems bad that it is getting higher with time.

Mxfrank · #2 07-02-2016, 07:58 AM

You also have fuel in the oil. It could be a worn engine, but maybe you're lucky and its a sloppy injector. I would switch back to Rotella and try one more test, just to be sure it isn't related somehow to the oil.

Clemson88 · #3 07-02-2016, 08:33 AM

If it were a sloppy injector wouldn't it be steady or getting worse? Can we eliminate the driving environment completely from this exercise?

Perhaps the Rotella is a better oil. It sure appears to be. I agree with Mxfrank only I'd give it two oil changes with Rotella and before I considered the results to be absolute. A database will be more comprehensive and complete as time goes on.

Oil which remains in the engine in various locations has a bearing on the next oil analysis too. Perhaps the volume of chrome in the old oil which remains in the engine is pushing the numbers up. Perhaps it's not. Time and more oil changes may put you more at ease though I do not know if it will alleviate the issue entirely.

pimpernell · #4 07-02-2016, 11:58 AM

Quote:

Originally Posted by nelbur

We have a '97 E300D with 245,000 miles. This is a NA diesel. For the last three 7500 mile oil changes I have tried three different 5W40 synthetic oils and had them analyzed thinking I would see which had the lowest wear metals. I was surprised to find that my chromium was three to four times the normal level, while the iron was very normal.

Blackstone thinks the chromium comes from the rings, but I cant figure out how they are wearing without the iron being high as well. With the engine idling, there is little blow by coming from the open oil fill hole, and no strange noise. The engine sounds the same as when I bought it 50,000 miles ago from my neighbor. Mileage is good. At idle there is a bit of nailing on one cylinder which I have thought was probably an injector. I am not aware of any injector work on the car.

The car is in good shape with no rust. It is garaged and the wife loves it. I haven't told her about the chromium. Given it's age and mileage, if the engine went bad I would likely look for a junkyard engine rather than try to fix this one, but I would love opinions on what is happening to give the high chromium.

The oils used were; Delo 400 LE, changed out recently; Mobile 1 TDT, on the previous change; and Rotella T6, on the earliest change. The iron was 26 ppm; 22; and 26 respectively. The chromium was 13 ppm; 11; and 7. Seems bad that it is getting higher with time.

As you state in your question, "if the engine went bad you would not fix it", I would not be too concerned about the oil diagnosis. Chromium usually indicates piston ring wear, but it might be premature on your part to expect the engine to just "give up the ghost" overnight. As another poster mentioned, I would just keep an eye on it, stick with the Rotella and not be too overly concerned. If it gets to the point where the engine is having noticeable issues, which in my opinion could be many miles down the road, then it would be time to tell the wife. Good luck!!!

leathermang · #5 07-02-2016, 12:04 PM

I would stick to the Rotella ...
I do not believe in 7500 miles between oil changes where the working conditions are as harsh as inside our diesels..
I would use 5000 miles as the max... since you can spend a ' lot more' on oil , one third in this example , and come out way ahead considering the cost of replacing the engine.. IF wearing out from the inside did turn out to be the reason for the engine giving up the ghost...
If you are still doing tests.. why not trying Straight WT 40 in the Delo 400 ?

Dan Stokes · #6 07-02-2016, 02:12 PM

As a crusty old technician who worked with engineers a lot, I can tell you that there IS such a thing as too much data. Sometimes this data tells you little but leads to a lot of second-guessing.

I'm wondering if the synthetic oils contain chrome coming out of the bottle. Mercedes Diesels are not known for eating rings and that's probably the only place for chrome to come from unless it's in the oil in the first place. And if the rings were going away you would get lots of iron in the oil as the bores are softer than the rings.

The suggestion to run a couple of changes of Rotella dino oil and check again makes sense if this result is costing you sleep. Otherwise, I'd run it 'till it dies, which will likely be a LONG time from now.

Dan

leathermang · #7 07-02-2016, 02:23 PM

Quote:

Originally Posted by Dan Stokes

.... And if the rings were going away you would get lots of iron in the oil as the bores are softer than the rings.........Dan

Except in small air cooled engines where sometimes a Chrome Ring is used to ' refurbish a bore' without taking the engine apart..
I believe the rings are designed to be softer than the bore so they wear into a good fit ..

97 SL320 · #8 07-02-2016, 06:35 PM

Chromium is a hard metal, I wonder if the timing chain is coming apart? Perhaps the rollers have a high chromium content.

Maybe a ball bearing is coming apart.

I'd also investigate the liners if this engine uses them, they can have a high chromium content but , from what I recall, you can't use chromium rings and a high chromium bore at the same time, they will gall.

I would not blame a name brand oil for wear. You should be able to pull a tech sheet on the oil to see what new oil looks like but I really doubt chromium would be added to an oil.

nelbur · #9 07-02-2016, 08:03 PM

I appreciate the comments. Keep them coming. I am now running on Rotella T6 again to see if the climb in chromium is related to running time or to the oil used.

The nature of the driving has not changed. It is primarily city driving.

The recommended oil change interval is 7500 miles. I assume city driving would be considered hard service, and would use a shorter interval on dino oil, but with synthetic 7500 seemed reasonable for a diesel. If iron had been high I would think the interval might be too long, but that is not the case. The problem is chromium specific, apparently.

Since I change my own oil I get out all that can reasonably reached. I park with the front low and suck with a tube down against the pan. I even suck out everything I can from inside the filter housing.

I was using Mobil 1 before this experiment. The surfaces visible through the oil fill hole were clean but had a brass like yellow look to them. One change of Rotella T6 cleaned off whatever made things yellow. Pennsoil says they make Rotella T6 for Shell. I'm surprised Shell would allow Pennsoil to mention that Shell contracts it out.

It seems like wear of a high chromium steel would give high iron and chromium. Even if the rings have a chromium layer on the wear surface, it would be wearing against the steel liner and I would expect increased iron. I don't understand how chromium can be the only high wear metal.

leathermang · #10 07-02-2016, 08:34 PM

Quote:

Originally Posted by nelbur

...The recommended oil change interval is 7500 miles. .......

By people who sell oil ... or synthetic oil substitute.

Not by anyone , who if they have participated in what business advertising calls puffery...

may have over estimated how many miles the oil will provide proper lubrication....

will reimburse you for any loses you suffer due to their overly optimistic claims.

97 SL320 · #11 07-03-2016, 06:05 AM

I don't call 7,500 miles too far. The engine uses lots of oil ( 7 QT ? ) so it will take longer for oil to wear out. And, what do the other oil quality numbers say about oil life?

nelbur · #12 07-03-2016, 10:47 PM

Quote:

Originally Posted by leathermang

By people who sell oil ... or synthetic oil substitute.

Not by anyone , who if they have participated in what business advertising calls puffery...

may have over estimated how many miles the oil will provide proper lubrication....

will reimburse you for any loses you suffer due to their overly optimistic claims.

LOL, non of the above. The MB Maintainance Booklet that came with the car specifies, "Lubrication Service (oil and filter replace) every 7500 miles". But I understand where you are coming from. After I finish this experiment, I will switch to 5000 mile intervals which I am more comfortable with, especially given the high chromium.

Jeremy5848 · #13 07-03-2016, 11:45 PM

My '96 E300D (W210, OM606NA), essentially the same car as the OP's, had a chromium "score" of 2 from Blackstone at 4000 miles on the oil and 301,000 miles on the engine. This car doesn't get driven much so I change oil more often (distance-wise), about once a year. Chevron Delo-400LE Synthetic (group III, not a "true" synthetic).

OTOH, my '95 E300D (W124, OM606NA) at 7000 miles on the oil and 220,000 on the engine had a chromium score of 7 and Blackstone allowed it was high enough to be worth keeping an eye on it.

Jeremy

leathermang · #14 07-04-2016, 12:22 AM

Quote:

Originally Posted by nelbur

LOL, non of the above. The MB Maintainance Booklet that came with the car specifies, "Lubrication Service (oil and filter replace) every 7500 miles". But I understand where you are coming from. After I finish this experiment, I will switch to 5000 mile intervals which I am more comfortable with, especially given the high chromium.

That owner's manual was given to you when the car had almost no miles on it.. now it has a Quarter of a Million Miles on it....

On my cars... being an old guy set in my ways.... I go to straight 40Wt oil on my cars after 100,000 miles...and on gas engine cars I also changed out oil pumps at that interval.....
the proper thickness of oil in worn spaces... and the ability to pump into all of the those spaces all the time...
The oil pump is the heart of the engine...and the oil its BLOOD... and so much cheaper than redoing the hard parts of the engine in a rebuild....

nelbur · #15 07-04-2016, 11:14 PM

jeremy, it is interesting that you should have different results on two examples of the same engine that I have. I assume that the '95 has the same valve train set up, right? Were you using biodiesel on both? I was wondering if it would lube the rings a bit. Are both of yours treated about the same as to the nature of their driving, the type of oils used, etc.? On the oil analysis with high chromium, was the iron low or high? Sorry for all the questions, but I was a scientist in an earlier life and I just have to try and figure out the solution to a problem.