Incredible disappearing, reappearing oil! - PeachParts Mercedes-Benz Forum

BluEyes · #1 10-29-2005, 12:09 AM

Well, I've read about this happening in Benzes with synthetic oil, but never had it happen to me before.
I check my dipstick pretty regularly, especially since it has gotten cold and I am paranoid about burning oil while the engine is cold (it sure makes enough smoke). The dipstick had been reading pretty regularly at about 1/2 for months, untill monday at school I checked it and it was right at the bottom mark!

No time to get oil, no spare oil, had to go to work, figured I'd check it again after work. After work it was the same. I know it should be okay since it was not below the low mark, but the poor 220 has to turn 3200rpm for 35 miles home, so I went to walmart to buy a quart of 5W40. I checked the dipstick for the third time that day after buying the oil and it still read the same, so I poured in 1/2 quart.
The next day the dipstick read at about half, which made sense, and I was kinda starting to think that I had just been having some oil burning on cold starts. That was untill today when I checked the oil before leaving school. Today the dipstick read completley full!
So,

? I'm not complaining, since it seems that I am NOT burning oil after all, but is it usually this bad? Really, this seems like my dipstick has been reading lower than actual all week! The odd thing is that I have checked it earlier this week after sitting overnight and it only read 1/2, but today when it read full, the car had only been sitting for about 5 hours. Is it normal for the reading to change like this for no apparent reason?

DieselAddict · #2 10-29-2005, 02:18 AM

Changes in oil temperature and car tilt can play tricks on you. When checking the oil you need to be sure the car is on level ground and the oil is hot, but don't check it immediately after shutting off the engine. Give the oil a few minutes to drain to the oil pan.

Tangent · #3 10-29-2005, 05:17 AM

also if you have just shut off the engine there still about a quart of oil in the oil cooler and some in the filter

BluEyes · #4 10-29-2005, 10:58 AM

How does oil temp affect the dipstick reading? I know things change volume with temperaure, but it's not that much!
Typically I check the oil after the car has been sitting overnight, so the oil is stone cold, but has had many hours to drain back. I can't see the oil going anywhere after it has drained back to the sump, so would 1 hour later or 10 hours later make any difference?

My driveway where I check the oil is very nearly level, but what confuses me is that when I checked the oil at school last, the car was on a slight upward grade. Since the dipstick is near the front of the engine, this would seem to make the reading come in a bit lower than actual? But, it was my highest reading all week.

kerry · #5 10-29-2005, 11:12 AM

I experienced similar anomalies with my 307d with a 616 engine when I owned it. It had no oil cooler. I was never able to account for it satisfactorily. One possibility is that the oil drained down from the filter since it is higher than the sump, but this is far fetched I think.

Brian Carlton · #6 10-29-2005, 11:56 AM

Quote:

Originally Posted by BluEyes

My driveway where I check the oil is very nearly level, but what confuses me is that when I checked the oil at school last, the car was on a slight upward grade. Since the dipstick is near the front of the engine, this would seem to make the reading come in a bit lower than actual? But, it was my highest reading all week.

The level of the vehicle makes a dramatic difference in the level on the stick. Slight changes in level, which you may not even see, can easily change the level on the stick by 1/4".

See if you can duplicate the results at school. Check the oil, carefully, in your driveway, and then again after sitting a few hours at the school. Make sure you park it in the same place, if you can.

It does seem like an anomaly. The level should be lower on an upward grade.

whunter · #7 10-29-2005, 12:09 PM

Before you wreck your engine!!!!!!!!!

Run away diesel, why does it happen?
Run away diesel, why does it happen?

Ralph69220d · #8 10-29-2005, 03:32 PM

check the manual to see if and how many check valves there are to keep the oil main lines from draining back into the pan. many vehicles use check valves to ensure immediate oil flow to crank/cam etc immediately upon starting.

Hatterasguy · #9 10-29-2005, 08:09 PM

Letting synthetic drain overnight is critical to getting a proper reading. Also try to check the oil when the car is in the same spot, ie where you park it at home works.

I have noticed that if my car is tilted slightly backwards I will lose about 1/2 a quart on the dipstick. But if I level the car out it magically comes back!

68882 · #10 10-30-2005, 01:43 AM

Other lists have noted that if you use Mobil 1 synthetic oil, it can take upwards of 7 hours before you get an accurate reading. There is thought that because of the way the molecules work (polar alignment) they are sticky and stick to metal so the time for *all* the oil to drain into the crank case is long. Remember the oil manufacture is trying to ensure a film of oil is left on all surfaces for later cold starting purposes.

BluEyes · #11 10-30-2005, 09:31 PM

Well, the car hasn't run since last night, roughly 20 hours ago, and the oil is currently reading a bit over 1/2. Driveway isn't perfectly level though, but close.
I have read about the behavior of synthetic oils before, that's why I only added 1/2 qt when the engine was at the low line, I was suspicious of the reading being off and didn't want to overfill.
I am still at a loss to explain the full reading I got before though... Maybe it was at just the right angle to cause more oil from the filter or cooler to drain back than when the car is level?
I haven't seen any mention of checkvalves in the manual, but I believe there should be at least one. I find the layout of the manual a bit confusing though, so I might have just missed it.

I have read the entire runaway engine thread. I still believe that the OM615 having a TB would at least keep the engine from running away to the point of destruction because there just wouldn't be enough air coming through. The TB is almost as closed as one on a gas engine at idle. But, if I'm wrong about that, the car has a manual trans so I can stall it out if need be.

whunter · #12 10-31-2005, 01:13 AM

Quote:

Originally Posted by BluEyes

Well, the car hasn't run since last night, roughly 20 hours ago, and the oil is currently reading a bit over 1/2. Driveway isn't perfectly level though, but close.
I have read the entire runaway engine thread. I still believe that the OM615 having a TB would at least keep the engine from running away to the point of destruction because there just wouldn't be enough air coming through. The TB is almost as closed as one on a gas engine at idle. But, if I'm wrong about that, the car has a manual trans so I can stall it out if need be.

Many people on the forum run their vehicles up to 1/2 quart low on the dip stick.
The dip stick is not a precision measuring instrument, only a rough field guide.
What you should do at the next oil change is level the car, remove the filter, drain the oil, new filter and exact OEM oil quantity, run it for five minutes, turn it off for 12 - 24 hours, check the dip stick and mark the stick for that level, do not add more to bring it up to full level on the stick, only your mark level.
Check the level same vehicle location every time for a couple of weeks.
If you over fill the crankcase, it will splash and vaporize = get blown out.

Brian Carlton · #13 10-31-2005, 07:24 AM

Quote:

Originally Posted by whunter

Many people on the forum run their vehicles up to 1/2 quart low on the dip stick.

Some people run the vehicle at 1 quart to 1.25 quarts low.

Hatterasguy · #14 10-31-2005, 09:30 AM

Yeah Brian I finally figured out why your engine stops buring oil. Because it runs out of oil to burn!

Brian Carlton · #15 10-31-2005, 09:50 AM

Quote:

Originally Posted by Hatterasguy

Yeah Brian I finally figured out why your engine stops buring oil. Because it runs out of oil to burn!

I wouldn't care if it burned it. But, best I can tell, it leaks it. And, as you know, the smell of Rotella-syn seems to be pervasive......in the cabin.......in the trunk.

But, when I run it low........the entire problem is very much reduced.