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I've read the prior threads about checking the oil when the car is warm, waiting, level ground, etc.

What I don't understand is that when I leave the beast to sit for a few days and check the oil level stone cold, it reads lower than when I check it hot. How can this be? After leaving the beast for a few days doesn't it have a chance for all the oil to drip down into the pan from the cylinder heads? If that's the case, shouldn't the reading be higher cold than when warm?
 

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Silverstreak said:
I've read the prior threads about checking the oil when the car is warm, waiting, level ground, etc.

What I don't understand is that when I leave the beast to sit for a few days and check the oil level stone cold, it reads lower than when I check it hot. How can this be? After leaving the beast for a few days doesn't it have a chance for all the oil to drip down into the pan from the cylinder heads? If that's the case, shouldn't the reading be higher cold than when warm?
I get the same reading and have wondered the exact same thing - maybe someone can explain this to BOTH of us.
 

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Engine oil expands when it is hot, more so than the amount of oil that is uncollected. If you have a motorcycle, Look at the glass eye before and after a ride. You should notice that the upper third before the ride is empty, but completely covered after.
 

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tranck said:
I get the same reading and have wondered the exact same thing - maybe someone can explain this to BOTH of us.
I am wondering what would happen if we etched a mark on the dipstick to show oil level when cold (after confirming it is full up on hot measurement). Then it would seem very easy to check cold and get very repeatable results. Am I missing something here?
Regards,
Jerry
 

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gsfent said:
I am wondering what would happen if we etched a mark on the dipstick to show oil level when cold (after confirming it is full up on hot measurement). Then it would seem very easy to check cold and get very repeatable results. Am I missing something here?
Regards,
Jerry
Sometimes auto trannies have hot and cold level marks- should work, provided your 'cold' is a constant temp...I seem to recall however, that there is usually a 'preferred' temp - warm I think.

I personally think it is one of those things that a particular mfg comes to over time and analysis: what is a more repeatable 'condition'? Shut down plus 1 minute, or 'cold'? My cold these days is 75F. In the winter it will be 45F. For the boys in the NE, cold will be -5F come winter...

My guess is that BMW engineers envisioned drivers pulling in to refuel, starting the pump, then checking oil...

BTW- most garage floors have a slope (per building code) so that water will flow out. Is this enough to change the reading? Probably, but not significantly. As long as that is where you measure it all the time, that is really all that mattters- a mm above or below is probably fine. :)

A
 

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ard said:
Sometimes auto trannies have hot and cold level marks- should work, provided your 'cold' is a constant temp...I seem to recall however, that there is usually a 'preferred' temp - warm I think.

I personally think it is one of those things that a particular mfg comes to over time and analysis: what is a more repeatable 'condition'? Shut down plus 1 minute, or 'cold'? My cold these days is 75F. In the winter it will be 45F. For the boys in the NE, cold will be -5F come winter...
That makes sense. Of course, there is warm and hot. In the middle of summer, my oil will be hotter and thinner when I stop to check (90+ degrees outside) then in my winter (50-60 degrees outside), so it works both ways, although not as extreme with heat, probably only a few degrees difference.

My guess is that BMW engineers envisioned drivers pulling in to refuel, starting the pump, then checking oil...
I agree. Same idea, pull into garage, shut of motor, open hood, go get rag. By the time I get back to pull dipstick for reading, it is about a inute or so since the motor was turned off.
Regards,
Jerry
 

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Actually, I am glad to read that the level is lower after sitting. This means the oil is staying where it is useful--in the engine internals, not the oil pan.

Expansion or contraction? I haven't a clue as to whether oil can actually change size that much. But from 200° back to 50° well....:confused2
 

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One wonders whether BMW could not have come out with a simple chart of temperature verses oil level so that we could check our engines whilst cold when at home. After all the instruction book is not exactly small is it?

Am I the only one who finds it a little embarassing checking the oil in the garage thinking that eveyone else is thinking "huh he may have a Motorsport but it is not working very well, he has an oil leak" ..........?

There must be more to it ?????? .

Pip
 

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Why not try filling a large measuring cup, or better yet a tall beaker, with engine oil @ room temperature, then toss it in the oven set @ 220 degrees F for an hour, and see if the level changes. Of course, try this only when the wife is away!

Eric
 

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From a post at Bob Is the oil guy:

My physics book gives V = V0(1 + B(T1 - T2)) and B for petroleum as 0.000899/ degree C. Different oils are going to vary, it gives B = 0.000745 for ethanol. If your oil goes from 70 F to 250 F the volume will increase by V = V0(1 + 0.000899(100C)) = V0(1.0899). 4 quarts times 1.089 = 4.356 quarts. "

So a 100C or 180F rise is around 8.9% volumetric change...


A
 

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My guess is that the most repeatable and accurate oil readings were found to be following the directions in the manual. I am guessing they are less reliable when cold. Otherwise, why would the engineers have come up with such a detailed, specified routine? It is certainly different from most other cars, and takes more work to get an oil reading. There would be no other reasons that I can think of.
 

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10/60 is a thick oil, a bit 'o heat would expand it and give an accurate reading on the stick IMHO. The idea of checking your oil when re-fueling also makes a lot of sense. BMW engineers, what will they think of next:1:
 

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If I remember correctly the S62 engine has a semi dry sump design. In a true dry sump like my old 911 and Ferrari Boxer you checked the oil with the engine running at operating temp) Now (like a dry sump) the S62's scavenge pumps draw more oil than than is returned to the oil pan, with the volume of oil making sure that the pump is kept submerged.

If you were to check the engine cold you would get a false reading that is too high, due to the fact that oil has had the time to drip back into the oil pan. The process of idle 15 sec then shut down and wait 1 min. then check oil seems overly complicated, and was probably planned so that BMW would not have had to design and manufacture and stock a different dipstick for the S62.

Just my 2 cents

Peter M
 

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You find reading the oil level of the M5 complicated, have any of you tried to read the level of a Porsche 911 carrera (aircooled) first you have 11 liters of oil and second if you read engine off you have nothing on the dipstick. This leads to novices adding and adding oil and then breaking there engin. And when you run it cold, the level is way bellow level. It needs to be at running temp. means about 15 minutes of driving. It takes some getting use to.
 

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Hold on, you were beginning to make sense until you said, "If you were to check the engine cold you would get a false reading that is too high". Don't we all agree that when checking the S62 cold, it will read too LOW?

PeteM1965 said:
If I remember correctly the S62 engine has a semi dry sump design. In a true dry sump like my old 911 and Ferrari Boxer you checked the oil with the engine running at operating temp) Now (like a dry sump) the S62's scavenge pumps draw more oil than than is returned to the oil pan, with the volume of oil making sure that the pump is kept submerged.

If you were to check the engine cold you would get a false reading that is too high, due to the fact that oil has had the time to drip back into the oil pan. The process of idle 15 sec then shut down and wait 1 min. then check oil seems overly complicated, and was probably planned so that BMW would not have had to design and manufacture and stock a different dipstick for the S62.

Just my 2 cents

Peter M
 
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