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What is considered too much oil consumption?

7K views 12 replies 8 participants last post by  Buaioeae 
#1 ·
I have a well used but strong running '81 300D with 210k miles. She has gone through a couple owners so I can't speak specifically to the quality/frequency of the maintenance but I know between the previous owner and I, over the past 50k miles there have been regular 3000 mile oil/filter changes and routine PM done.

It's currently burning about 1 quart every 500 miles and has for as long as I've had it.

With 1 quart per 500 miles, can the motor still be considered healthy for the miles and have another 100k in her? or is she nearing the end?

Very minor leaking. A few drops under the car when parked for a whole day so the oil is being consumed not leaked out.
 
#3 · (Edited)
So, is it leaking or is it using oil? There's a bit of difference regarding the condition of the engine. The leaking is usually due to age; using is due to wear.

You know what they say about old mercs....if it stops leaking oil, start worrying.
:D
I've never heard that said about any Merc, not even old Mercs. But I have heard it being true about British cars, even new British cars. Yes, even Rolls-Royce.
 
#4 ·
I got a 82 240D that burns that much too! 225K miles but strong and stubborn as a mule...:grin

I've done some research on why mine burns that much (sometimes even more) oil and some say its the Valve stem seals or the little o-ring in the supply lift pump, but to suspect that o-ring is to see if your fuel is contaminated with oil (by checking your pre-filter and see if its a greyish (?) color)

However, I've noticed for me if I had a bottle and a half of STP oil additive during an oil change, it'll take 1000 miles before I have to add any oil, so give that a try and see if adding some kind of oil additive helps it consume less. If it does, I wanna say its valve stem seals or rings... I also hear that doing a leak down test will answer most questions :smile
 
#10 ·
My 78 300CD, burns about that same amount of oil 1Qrt/500miles , at interstate speeds 75/80 MPH. Less at the lower speeds that I usually drive. It is not leaking the oil, so has to be burning it. I have replaced my valve stem seals, and that has not improved the loss of oil. While replacing seals, valve stems seamed to be fairly loose. Have also tried using oil additives, they lessened the oil usage, but they thickened the oil enough that I have a hard time getting car to start below 30F. Changed oil, not adding any additives, and it now starts right up at 30F, and below. The car sat for several years before I got it, and was hoping oil usage would go down as I ran it. WRONG, Engine has 255K miles on it, and I am guessing the rings/head are just worn out:crying

Luckily, Many OM617's were built, so currently looking for a lower mile donor:wink
 
#6 ·
If it leaks oil slowly when standing, it will leak oil more quickly when under pressure. Besides, leaks are easier and cheaper to fix. I'd follow whiranrat's recommendation, then I'd fix the most likely leaks - lower sump gasket, drain plug, valve cover gasket - and see if it makes a difference.

If an engine pulls strongly, it's unlikely that it's worn enough to use a significant amount of oil. My first 240D was so worn that she had to be towed to start, and she still didn't use oil. By contrast, my 300D starts and shuts down with authority, but the lower sump is leaking about 2 quarts every 3k-4k miles. (I'll fix that during the next service.)
 
#9 · (Edited)
If it's using oil, it's not seals, it's worn bores, the oil becomes part of the combustion process (as I understand it), a thicker oil is less likely to get past the piston rings.

You don't say what oil you use, I use the synthetic Rotella 5W40, but if I was doing a lot of highway, I have a conventional 15W40, that I buy from the local farm supply place at $15 for 2 gallons. That should get you there at a quart per 500 miles :D

This dependent on the temperature range you'll be seeing on your trip of course.

http://www.ruralking.com/rural-king-heavy-duty-diesel-engine-oil-15w40-2-gallon-75072.html
 
#12 ·
You might see how much blow by you have by removing the oil fill cap when it warm. If the stream looks like a train, the rings are probably worn.
I believe this has a lot to do with prior oil changes or lack thereof. My 85 300 CD uses about one half quart in 4000 miles and I have maintenance records way back to the early nineties. Even in cold weather there is very little smoke upon starting and no white smoke on acceleration. Virtually no blow by either.
 
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