Oil change

[Gilbey]

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Good morning all,

I'm being told that when they drain your engine E 220: Diesel for an A service there remains in excess of a Pint of the old oil left behind in the Galleries and oil runs that then gets mixed with the new oil.. Is this the case and is it OK.
Why can't they remove all the bold oil.

Thanks​

 

[190]

It's inevitable that some oil will remain and that on a diesel because soot is such an effective dye this residual oil will blacken the new oil almost immediately.

If you want to get technical there is a strong augment among oil professionals that a little residual old oil is a good thing due to the high detergent content of the new oil stripping of the anti-wear coating from the bearing surfaces. Unlikely as it may seem this has been backed up by measured wear rates.

 

[bob6600]

Use an engine flush if you have concerns

 

[190]

I would only flush an engine using good quality oil. If the engine needs it i.e. it's a old and sludged up then there is a case for proper flushing oil followed by more frequent oil changes but it's best not to let it get in that state in the first place.

The dilemma of using cheap flushing oil is that the pint of oil that's left behind is now cheap crappy flushing oil that will get mixed with the MB spec new oil. It's better to have the pint of old quality oil mixed in even though it looks dirty.

 

[Gilbey]

Thanks all. Still not quite answering my problem. Should this " small " amount that might be left be more than a pint?

Thanks again.

 

[PobodY]

You could always flush under no load, then run some cheaper oil through to get it out, then refill with your chosen grade.

I frequently run a little oil through from filler and out the sump before putting the plug back in and refilling it. - When it goes (reasonably) clear then I've got rid of most of the muck.

Don't forget the oil filter.

 

[190]

Thanks all. Still not quite answering my problem. Should this " small " amount that might be left be more than a pint

I would have said less than a pint. The oil filter is a good design that on removal allows all the oil that it contained to drain down into the sump. That only leaves oil in the pump and galleries plus any that remains in the sump. I can't see that adding up to more than a pint.

When I changed my own oil using a vacuum extractor, which is what a dealer would use, I carefully measured the volume that came out and it was at least 0.5 litres more than the "book" oil change quantity. That lead me to believe there couldn't have been much left behind.

 

[PobodY]

You'd think that the galleries would be designed to drain back to the sump, so I agree that it shouldn't be much that is "stuck" in the engine after a change.

 

[190]

The galleries are small enough that surface tension will retain the oil and it would also have to drain back through the pump. You don't really want the oil to drain back as that would cause a delay at start up before oil reached the bearings.

I'm curious to know why you are concerned about the volume of old oil that remains. I've spent 45 years changing my own oil and have always been **** about getting the last drop of old oil out even to draining them overnight. Never being too old to learn I've recently been convinced by oil professionals that it's not necessary and may even be a bad thing because of the reason I mentioned in my first post.

 

[Gilbey]

Hello 190

The history behind this is that I checked my oil after only a mile or so and it was black already...the dealer told me it is because the galleries etc retain just over a pint of the old oil...
I found this hard to understand. Thinking they were not changing the oil or not allowing it to drain long enough.
Would still welcome opinions.
They also said it was because it was a Diesel, although I had the same issue with my 200 petrol a year earlier. That's why I checked after a short distance.
Thanks to all for your input.

 

[brucemillar]

The history behind this is that I checked my oil after only a mile or so and it was black already...the dealer told me it is because the galleries etc retain just over a pint of the old oil...
I found this hard to understand. Thinking they were not changing the oil or not allowing it to drain long enough.
Would still welcome opinions.
They also said it was because it was a Diesel, although I had the same issue with my 200 petrol a year earlier. That's why I checked after a short distance.
Thanks to all for your input.

All that you have been told is correct and not an issue.

"a pint" that is using the UK standard of measurement? usually a football pitch or five mini's or in the case of most blokes 8 inches.

I suspect that they really mean that "some" old oil will will remain due to it sticking to the innards or lying in galleries. As it remains then it would be difficult to measure how much that actually is.

The same is true when you replace ATF you are only draining the box and not the TC so roughly 50% of your ATF is always "old" stuff. This is unless you specifically state and pay to have the TC drained.

 

[Yugguy]

It's nothing to worry about. And diesel oil goes black very quickly anyway due to it holding soot particles in suspension. Which is by design and what you want it to do.

There are 1.7 pints in a litre, so on a 7 litre change even a pint remaining still changes 11/12 of the oil - or to put it another way 92%

 

[MancMike]

You'll never get rid of all the old oil. No matter how many oil changes you perform, it'll always have a diminishing percentage of the old oil left.

I don't know why you're so worried about a small amount of old oil. It's as if you think as soon as your new bottle of oil arrives, your old oil turns into an abrasive. It's been running your engine just fine 100% old oil, and is then mixed with lots of lovely new oil.

 

[Gilbey]

Thanks to everyone for your valued input.

 

[Gilbey]

One more question. Is there an easy way to find ones own post? I seem to get there in the end but don't quite know why.

 

[190]

At 4 millionths of an inch give or take an order of magnitude, the soot particles in a diesel engine are vastly smaller than the filter media pores so they are not filtered out and remain in suspension in the oil. Being so small they are an extremely effective dye and will turn the new oil black even if there is very much less than 1 pint of old oil remaining.

The issue you had with your petrol engine is not right though. The new oil should remain clean for some time and if was dirty after a change then they did leave too much old oil in.

To find your own posts you can use the advanced option in search which allows you to search by username or you can just right click your name in the left hand pane of any of your posts and select "find more posts"

 

[PobodY]

You can also watch the thread, that way you get an update when someone adds to it (and it's easy to find in your list of watched threads).

 

[bob6600]

One more question. Is there an easy way to find ones own post? I seem to get there in the end but don't quite know why.

This should work for you

http://www.mbclub.co.uk/forums/search.php?searchid=9734159

 

[E55BOF]

Just left click on your username (top right on whatever page you happen to be on), then on 'Statistics' in your profile, then 'find all posts by'. Simples.