I'm a bit farther along in the failure process. I'm at a quart every 300 miles and it has been holding at that for the last 6000 miles, currently I'm at just over 160K miles. I bought the car at 130K miles and it was using a quart every 2000 miles. Just watch your consumption. A quart per 3000 would be normal and acceptable for many 603's.

I did a compression check recently and the cylinders were all in the 420-450 range if I remember correctly. The car starts and runs great, it just kills all flying bugs as it goes by. So that doesn't seem to be an indicator of wear in my case. Do others have different observations?

Chuck

I have an 87 300D with the 603 engine that uses about 1/4 quart per 5000 miles. The engine has at least 187,000 miles. More likely 235,000 miles.

I purchased a 95 S350D 3-4 weeks ago. It has 230,000 miles on it. I've put about 2,000 miles on it and have used about 1/8 of a quart.

I'm watching and preparing for an "eventual" engine issue.

Lampbum2 your 350SDL went from 1/2 quart per 5000 miles to 1 quart per 3000 miles in 78,000 miles.

To compare apples to apples you went from 1/2 quart per 5000 miles to 1.67 quarts per 5000 miles over the period of 78,000 miles of driving.

Based on that I could have 78,000 miles or so left in mine. (I could have a little less or a lot more. Hopefully a lot more.)

-Jim

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1995 S350D, Green with black leather interior.
Bought January 2008 w/ 233,xxx miles.
I did 22,000 miles during the first year of ownership.

Makes me curious, we need an oil useage thread.

__________________

Gone to the dark side

- Jeff

Oil burnt and oil dripped hard to equate!

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82 300D....went to MB heaven
90 350 SDL....excercising con rods

I would perhaps check for leaking turbo bearings. When consumption reaches your quoted levels compression should already be down to some extent on a bad cylinder in my opinion. Remember on most examples of these engines all the oil burning or the majority of it is being fed through one cylinder. Feeding a quart through one cylinder every three hundred is about the same as an overall burn rate of 50 miles per quart if all cylinders had equal problems.
This type of rate would normally be consistant in most cases with an engine with sub standard compression. Of course this is just an opinion and probably wrong as well. Although if it were my car a quick check of the turbo for leakage at the bearing seals might enter my mind. There are and always will be exceptions to any general concencious.

1 quart every 3k miles isn't much oil at all, hardly any.

When are you getting the blue smoke? It could be your turbo seals as well. Yank off the crossover and see how wet it is.


IMHO this is a huge waste of time and money replacing what is a perfectly fine motor. That engine could keep right on needing one quart every 3k miles for the next 100k+ miles.

If you get a good deal on a 3L wait until you need to add a quart every 300 miles.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

I am working with a friend who is a great mechanic, but primarily familiar with domestic cars. He refuses to believe the car can run as well as it does and has good compression, adn still have a lower end issue. We started an exploratory tear down in August and found a leaky turbo. It was rebuilt and oil consumption is slightly better but still in the 300 miles / qt. range. His next thought was valve seals or there may be a stuck ring. I have tried 2 doses of engine flush, new oil change, and then used seafoam. I am mid way through the second 3000 mile oil change with seafoam. All appears to be staying the same. I have been typically adding about 8 quarts ( plus the 2 it goes low before I add) over the 3000 miles. There are very minor leaks, but not 8-10 qts worth.

On another site a person actually took apart a bad 3.5L and found the bent rods and the pistons tipped in the cylinder, so a top edge and bottom edge of 2 pistons were worn. This allowed the leakby on the rings. He found his cylinders only very slightly out of round. A thousandth or 2 I think, it might have been 3 or 4.

So I think my next move is head removal and look for tipped pistons. Sixto found this on his 3.5 liter he took the head off, but I don't think he actually took apart the block to see the cause.

Again, any more suggestions or sharing of symptons to help us all understand this would be wonderful.

Chuck

Chuck,
Sounds like we are at a similar place with our cars. I just posted recent history and headgasket replacement on my car on thread entitled "Oil Useage Poll".
JT

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JT
1991 350SD 216,000

Hi,
I can't belive a compression test will help me at this point, The car starts and runs fine, it is using oil, my motor is dry, there is a bit of oil at the rear main seal, just moist is all, there are no leaks.
I feel lucky to have 244,000 miles from this motor, some didn't make it to 80,000 miles, I belive the history of these motors are telling me what I need to know, so I will purchase the 3.0 block and get it ready to install in my car.
Is there anyone on this sight that has personally rebuilt there 3.5 liter with success?
Jim

I am sure you can find someone who has, but you can also find folks with four hundred k on them without problems.....but you are doing the right thing in getting the three liter block.

Folks are just trying to be helpful in case you might not actually need to yet.

Tom W

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Yea, thanks Tom, You are right, everyone is being very helpful and I am being stubborn and looking at the history of these motors which provides a lot of facts and I want to have a motor I can depend on, So I think I will go with the 3.0 liter.
Thanks Jim

Does a 3.0L motor from a 86/87SDL bolt into a 90's 350 rod bender?

They are the same car.

__________________
1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Tell that to my S350D with the 3.5 and my 87 300D with the 3.0. Absolutely not the same car. To your point my S350D and an 86/87 300SDL are not the same care either.

-Jim

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1995 S350D, Green with black leather interior.
Bought January 2008 w/ 233,xxx miles.
I did 22,000 miles during the first year of ownership.

Well yeah yours is a W140, his is a W126, a 300SDL is a W126 as well.

A 300SDL and 350SDL are the exact same car except for a few minor features.

A 300D would be a W124 which is a totaly different class and car than the W140.

I think the 3L 603 is the .961??? and the 3.5 is the .970?? I need to whip out the FSM to see, but both cars are the W126.125. The only differance with the 603's are the blocks.

Regardless to what car its fitted in a 603 is a 603 and you can swap them around. The only major difference other then a few more electrical controls the W140's probably got, is that in the W124 the 603 uses a different oil filter housing.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200