Discussion
Here's a question about dipping the oil level on my E39 530d.
If I dip the oil level after the car has stood for some time I get a nice easy-to-read level line. If, on the other hand, I do what the handbook says I should remove the dipstick ignoring the reading, wipe it dry, replace it, remove it again and then read the level. Problem with that is that I now have two different levels, the first when the dipstick is pulled might be low but after wiping and redipping it is high, presumably because it has collected all the oil left in the tube when I first pulled it.
My head says to go with the first reading from cold when the oil has all settled nicely in the sump, but then I ask myself why have BMW been so specific about pulling, wiping and redipping.
Am I missing something? Which is correct please? Thanks in advance.
If I dip the oil level after the car has stood for some time I get a nice easy-to-read level line. If, on the other hand, I do what the handbook says I should remove the dipstick ignoring the reading, wipe it dry, replace it, remove it again and then read the level. Problem with that is that I now have two different levels, the first when the dipstick is pulled might be low but after wiping and redipping it is high, presumably because it has collected all the oil left in the tube when I first pulled it.
My head says to go with the first reading from cold when the oil has all settled nicely in the sump, but then I ask myself why have BMW been so specific about pulling, wiping and redipping.
Am I missing something? Which is correct please? Thanks in advance.
On my bmws the procedure has been to get the engine up to temp, allow it to cool down for 10-15 minutes then check the level. Something to do with allowing oil from various passageways to make it back into the sump I believe?
Have always removed the dipstick first to clean it then re checked on any car.
Have always removed the dipstick first to clean it then re checked on any car.
The only plausible explanation I can think of is to remove the effects of crankcase pressure differences.
When running, the crankcase is at negative pressure. After shutdown, that negative pressure will presumably equalise with atmospheric pressure.
If the dipstick tube is sealed from above by an o-ring, and from below by the oil level, then potentially the lower pressure trapped in the tube could cause the oil level to be pulled higher up the dipstick to create a false reading.
If the reverse happens - negative crankcase pressure, and positive pressure trapped in the dipstick tube, the oil would be pushed lower on the dipstick.
Removing the dipstick opens the tube and allows the pressure to equalise with atmospheric, meaning the oil level in the tube equalises with the sump to correct the reading.
When running, the crankcase is at negative pressure. After shutdown, that negative pressure will presumably equalise with atmospheric pressure.
If the dipstick tube is sealed from above by an o-ring, and from below by the oil level, then potentially the lower pressure trapped in the tube could cause the oil level to be pulled higher up the dipstick to create a false reading.
If the reverse happens - negative crankcase pressure, and positive pressure trapped in the dipstick tube, the oil would be pushed lower on the dipstick.
Removing the dipstick opens the tube and allows the pressure to equalise with atmospheric, meaning the oil level in the tube equalises with the sump to correct the reading.
Edited by BOR on Sunday 7th February 12:04
eezeh said:
On my bmws the procedure has been to get the engine up to temp, allow it to cool down for 10-15 minutes then check the level. Something to do with allowing oil from various passageways to make it back into the sump I believe?
Have always removed the dipstick first to clean it then re checked on any car.
It's to make sure the filter has a volume of oil in it. I had to add over 1/2 litre into my Z4 when it through a low oil warning depsite the disptick showing middle of the max & min on a cold engine.Have always removed the dipstick first to clean it then re checked on any car.
d_a_n1979 said:
On my M54; I check levels with the car level and stone cold...
Remove dip stick; wipe clean, re-insert, remove, check level and that's it...
Never had issues with inaccurate readings. Did the sale with my previous E65 730d (M57 engine)
This. It works. (Current BMW has the same engine as op’s).Remove dip stick; wipe clean, re-insert, remove, check level and that's it...
Never had issues with inaccurate readings. Did the sale with my previous E65 730d (M57 engine)
helix402 said:
This. It works. (Current BMW has the same engine as op’s).
First and foremost, thank you all for your contributions, appreciated!There is clearly a difference of experiences here, the dip, wipe and dip again produces a much higher reading on the second dip than the first for me. What has not emerged is a consensus as to what method works best for most. I think I'll just carry on chucking a bit in from time to time!!
Mike-tf3n0 said:
First and foremost, thank you all for your contributions, appreciated!
There is clearly a difference of experiences here, the dip, wipe and dip again produces a much higher reading on the second dip than the first for me. What has not emerged is a consensus as to what method works best for most. I think I'll just carry on chucking a bit in from time to time!!
I wonder if your dipstick works slightly loose when the car is running so it's fully home until you push it back in a few extra mm. There is clearly a difference of experiences here, the dip, wipe and dip again produces a much higher reading on the second dip than the first for me. What has not emerged is a consensus as to what method works best for most. I think I'll just carry on chucking a bit in from time to time!!
I don't think that is happening as it always takes one hell of a pull to extract the plastic ring pull bit from the tube. It's such a silly thing this but I worry that I could underfill or overfill depending on whether I believe the first reading from cold or the second after a wipe, both cases being potentially damaging.
Mike-tf3n0 said:
I don't think that is happening as it always takes one hell of a pull to extract the plastic ring pull bit from the tube. It's such a silly thing this but I worry that I could underfill or overfill depending on whether I believe the first reading from cold or the second after a wipe, both cases being potentially damaging.
What's the difference between min and max, 1 litre? So you're talking about maybe 1/4 or 1/8 of a litre out of a capacity of 6.5l (iirc). It is nice to get it just right but I'm not sure I'd be too worried. Good advice already above, such as try it warm, and especially don't worry too much. The oil level nag on the OBC wont even come on until you are at least 1litre below min level, and even that is set so it wont do damage providing its promptly addressed.*
the other thing I would add - try at a consistent location - the attitude of the parking bay/forecourt to level can account for a large amount of variation, yes a 1/4 measure easily - simply because the sumps plan area is large also; and having the car parked differently by a couple of degrees of angle fore-aft vs side to side does show.
I usually use the same set of pumps to fill-up, so if I'm going to - that's where I check oil level (and not on my street, with a 1:15 cross fall, or worse , depending on where I can park...)
the other thing I would add - try at a consistent location - the attitude of the parking bay/forecourt to level can account for a large amount of variation, yes a 1/4 measure easily - simply because the sumps plan area is large also; and having the car parked differently by a couple of degrees of angle fore-aft vs side to side does show.
I usually use the same set of pumps to fill-up, so if I'm going to - that's where I check oil level (and not on my street, with a 1:15 cross fall, or worse , depending on where I can park...)
- I ran an Alpina B10 3.3 manual for >5 years / 80Kmiles; oil top up I found mandatory every second tankful, on a perfectly healthy engine....
Edited by Huff on Thursday 11th February 18:19
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