Low oil from w/ dipstick on warm oil, but not cold…

[Chanman1029]

So I’m a little stumped right now.

recently I went to go for my monthly drive in my M3, and just about as soon as the oil reached operating temp, the low oil light came on. I turned around, took it back home and parked it. I was a little suspicious if the oil was actually low, bc I recently changed the oil about 1500 miles ago. So today, I checked the oil when the engine was cold, it was maybe 2mm below the full mark. I turned the engine on and let it warm completely up, at which point the low oil light came back on, shut it down, waited about 1-2 minutes, and inserted the clean dipstick and the middle of the dipstick is completely dry between the min and max marks.

I’m confused, I thought oil expands when its hot, so why am I reading almost a whole quart less when its hot? I know the element of human error still could exist, but this engine has 3k miles since its full rebuild to stock CR, CP pistons and rings obviously, block decked, head resurface and valve job, all machine work done by Lang. I assembled everything on the head from the cams up, and mated the block and head. I was very particular, but I suppose my only room for error on something that would affect oil levels would have to do with the head gasket(oem).

Is something disrupting oil flow? I cant imagine my oil is ACTUALLY low from consumption, especially after reading nearly full on a cold motor.

[Slideways]

So I’m a little stumped right now.

recently I went to go for my monthly drive in my M3, and just about as soon as the oil reached operating temp, the low oil light came on. I turned around, took it back home and parked it. I was a little suspicious if the oil was actually low, bc I recently changed the oil about 1500 miles ago. So today, I checked the oil when the engine was cold, it was maybe 2mm below the full mark. I turned the engine on and let it warm completely up, at which point the low oil light came back on, shut it down, waited about 1-2 minutes, and inserted the clean dipstick and the middle of the dipstick is completely dry between the min and max marks.

I’m confused, I thought oil expands when its hot, so why am I reading almost a whole quart less when its hot? I know the element of human error still could exist, but this engine has 3k miles since its full rebuild to stock CR, CP pistons and rings obviously, block decked, head resurface and valve job, all machine work done by Lang. I assembled everything on the head from the cams up, and mated the block and head. I was very particular, but I suppose my only room for error on something that would affect oil levels would have to do with the head gasket(oem).

Is something disrupting oil flow? I cant imagine my oil is ACTUALLY low from consumption, especially after reading nearly full on a cold motor.

After running the engine, the oil will circulate in the system and saturate the oil filter. The oil level will drop due to having less oil in the sump. The level should be in the middle after shutting off the car and waiting a minute. It sounds like your oil level is indeed low. Usually, the dipstick should be slightly above max when cold. Then it will drop to the middle when warm. If the oil level light is still coming on, the sensor is going bad.

Edit: Are you running a larger capacity oil cooler?

[heinzboehmer]

Oil sticks to components in the engine and takes a while to drain back down into the pan. When the engine is fully cold, the oil has had enough time to drain into the pan and thus reads higher on the dipstick.

Owner's manual says to check at operating temp, 1 min after shutting the engine off. So yeah, your warm measurement is the one you should go off of.

With that in mind, you probably need to add a liter or so into the engine (min to max on dipstick is about a liter or so). Do you remember how much oil you put in after your oil change? Mine usually takes about 5.5-6 L

[Chanman1029]

After running the engine, the oil will circulate in the system and saturate the oil filter. The oil level will drop due to having less oil in the sump. The level should be in the middle after shutting off the car and waiting a minute. It sounds like your oil level is indeed low. Usually, the dipstick should be slightly above max when cold. Then it will drop to the middle when warm. If the oil level light is still coming on, the sensor is going bad.

Edit: Are you running a larger capacity oil cooler?

I have a factory oil cooler.


and to answer heinzboehmer I filled it with 6L.

everything that was said about oil saturation makes sense, but I’m mind blown that all of a sudden I’m reading a whole quart lower from the cold measurement, that seems like a bit of an extreme deviation to me.

[heinzboehmer]

10W60 is stupid thick. Takes a while to drain back down.

Measure the oil level 1 min after shutting the engine off and then measure again ~5 min later. You'll see the level on the dipstick come up a good amount.

[Chanman1029]

Well if theres no disruption in oil flow, then what could be causing such aggressive consumption??

[heinzboehmer]

The disparity between cold and hot measurements (soon after engine shutoff) is not due to consumption. Some oil pools in the oil filter housing and sticks to the oil galleys all over the engine. This will eventually gravity drain back down to the oil pan, but it's not instantaneous. The spec for measuring level is 1 min after shutoff at operating temp, so measure based on that.

[Chanman1029]

The disparity between cold and hot measurements (soon after engine shutoff) is not due to consumption. Some oil pools in the oil filter housing and sticks to the oil galleys all over the engine. This will eventually gravity drain back down to the oil pan, but it's not instantaneous. The spec for measuring level is 1 min after shutoff at operating temp, so measure based on that.

thats what I did. I waited close to 2 minutes before reading the dip stick. Bone dry dip stick. My confusion is that I’ve usually always read the dipstick when its been cold, and its always been near the full mark, never has it ever thrown a light. Now all of a sudden, I’m getting a light and practically no oil indication on the dip stick.

oil saturation in the filter and oil lands makes perfect sense, and id expect to have a slightly lower reading due to it. But nothing is adding up here.

[Slideways]

Did you replace the oil filter housing? I believe there is a valve in there that drains oil back down to the sump after shutting off the engine.

A little off topic, but do the CP pistons work with the stock connecting rods?

[Chanman1029]

Did you replace the oil filter housing? I believe there is a valve in there that drains oil back down to the sump after shutting off the engine.

A little off topic, but do the CP pistons work with the stock connecting rods?

When i did the rebuild, I took that valve out to ultrasonic the housing, but I didnt replace the spring or the valve.

and yes, I’m using my OE rods with the CP pistons.

[Slideways]

When i did the rebuild, I took that valve out to ultrasonic the housing, but I didnt replace the spring or the valve.

and yes, I’m using my OE rods with the CP pistons.

Hopefully someone else can chime in, but I want to say that a good 0.5L of oil is in the oil filter housing before draining back down to the pan.

Do you have a part number for the pistons and do they come with rings?

[Chanman1029]

I dont have a part number unfortunately, I bought them from lang racing when I had them doing the machine work. Their website doesn’t list a part number, but maybe you could call and they could provide it.

but as for the original issue, can anyone confirm that reading the oil level after 1 minute of shut down should actually read within the min and max on dip stick?
i’ve always taken my readings on cold motors, and this hasn’t been an issue in the past prior to the rebuild so im concerned that something could’ve gone wrong along the way.

[Slideways]

It might be worth asking Lang since you bought some parts from them.

[heinzboehmer]

but as for the original issue, can anyone confirm that reading the oil level after 1 minute of shut down should actually read within the min and max on dip stick?

Yes, from the owner's manual:

[Chanman1029]

It might be worth asking Lang since you bought some parts from them.

I’m not mentally ready to hear him assume, “well it was probably an installation error”