[derrick603]

On the way home from work last night, my car complained that the oil was a quart low, so this morning, I added a leftover half quart of oil from my last oil change (I was planning to change the oil on Sunday, so no point in filling it all the way). Started driving and the car again complains that it's a full quart low. Thinking that the dipstick might be seriously off, I bought another quart of oil and poured in half of it. Started driving again and now the car says oil is completely full. No big deal, but what a waste of time and money.

[Delta0311]

Originally Posted by derrick603

On the way home from work last night, my car complained that the oil was a quart low, so this morning, I added a leftover half quart of oil from my last oil change (I was planning to change the oil on Sunday, so no point in filling it all the way). Started driving and the car again complains that it's a full quart low. Thinking that the dipstick might be seriously off, I bought another quart of oil and poured in half of it. Started driving again and now the car says oil is completely full. No big deal, but what a waste of time and money.

It takes a bit of time for the ECU to make the correct adjustments so you will get the oil pop up even after you pour it in. Overfilling is BAD, if the nav shows that you are over the fill line then I would do a oil change as soon as you can.

[ctuna]

There is a delay for the oil to update through the Sensor.
If you are adding it can take 30 minutes to and hour of driving for the
damm Sensor to update.

Its a good idea to look at the graph once in awhile to see what its
doing before it gets to the low indication.
Its good you only added .5 you should be fine.
You need to do two or three drives looking at the graph to get an
idea if it's really full.

[Efthreeoh]

The system updates at 5 minute intervals.

[evoix]

Originally Posted by Efthreeoh

The system updates at 5 minute intervals.

yup. takes a little time to report new reading accurately. Just another stupid feature. I missed having a dipstick.

[Efthreeoh]

OP, the sensor is also an oil quality sensor that allows for a safe and longer OCI, which ends up saving you money by needing less frequent oil changes.

[ThatRWD]

I think driving it rough might give it a better idea, when I changed my oil I put in 5, to test it, then one more because it said it needed one more. So I added that, drove for about 30 minutes, nothing. I knew it wasn't full because it takes 7, drove rough, staying at 3k-4k RPM, flooring it, it then told me it needs one more.

It's not the best thing in the world. I think they put it there so only people with seriously bad oil consumption problems would notice/complain.

[jwzimm]

Originally Posted by ThatRWD

I think driving it rough might give it a better idea, when I changed my oil I put in 5, to test it, then one more because it said it needed one more. So I added that, drove for about 30 minutes, nothing. I knew it wasn't full because it takes 7, drove rough, staying at 3k-4k RPM, flooring it, it then told me it needs one more.

It's not the best thing in the world. I think they put it there so only people with seriously bad oil consumption problems would notice/complain.

So you drove a car hard that you knew to be low on oil (as you did not put in enough in the first place)? Not a brilliant move IMHO.

[ThatRWD]

Originally Posted by jwzimm

So you drove a car hard that you knew to be low on oil (as you did not put in enough in the first place)? Not a brilliant move IMHO.

It's a quart for 30 minutes. Doubt it did any significant damage. Transmission will likely die way before the oil or oil type has any noticeable effect.

[ctuna]

OP, the sensor is also an oil quality sensor that allows for a safe and longer OCI, which ends up saving you money by needing less frequent oil changes.

It ends up saving BMW money

[derrick603]

Originally Posted by Efthreeoh

OP, the sensor is also an oil quality sensor that allows for a safe and longer OCI, which ends up saving you money by needing less frequent oil changes.

Is this true? As I understand it, the OCI is really determined by the amount of fuel used, not by any evaluation of the quality of the oil. Harder driving -> more fuel used -> shorter OCI.

[derrick603]

Originally Posted by ctuna

There is a delay for the oil to update through the Sensor.
If you are adding it can take 30 minutes to and hour of driving for the
damm Sensor to update.

I wonder why this is the case. It sounds to me like the oil level sensor should be pretty simple, it should be able to detect the oil level properly every time it checks (assuming the car is warmed up). Does this mean that if you had a catastrophic oil level failure (something punches a hole in your oil pan, for example, it would take half an hour before car knows something is wrong?

[derrick603]

Originally Posted by Efthreeoh

The system updates at 5 minute intervals.

I drove for 20 minutes after adding half a quart and it still said one quart low.

[jwzimm]

Originally Posted by derrick603

Is this true? As I understand it, the OCI is really determined by the amount of fuel used, not by any evaluation of the quality of the oil. Harder driving -> more fuel used -> shorter OCI.

The sensor has a quality sensor in it, yes. It uses the dielectric resistance of the oil to determine how much additive remains in the oil. Combined with other data such as driving habits and temperatures the computer determines when it is time to change the oil. It is actually pretty accurate. I had a sample of my oil analyzed from a standard OCI (about 12,000 miles) and it still had some active additive in it.

[derrick603]

Originally Posted by jwzimm

The sensor has a quality sensor in it, yes. It uses the dielectric resistance of the oil to determine how much additive remains in the oil. Combined with other data such as driving habits and temperatures the computer determines when it is time to change the oil. It is actually pretty accurate. I had a sample of my oil analyzed from a standard OCI (about 12,000 miles) and it still had some active additive in it.

Hmm, if that was the case, you shouldn't need to reset the OCI interval counter after an oil change, but you do. I didn't reset it last time and the counter continued counting down from the same number and at the same rate.

[jwzimm]

Originally Posted by derrick603

Hmm, if that was the case, you shouldn't need to reset the OCI interval counter after an oil change, but you do. I didn't reset it last time and the counter continued counting down from the same number and at the same rate.

Like I said, it does not only rely on the sensor. If you don';t tell the car that you changed the oil it will not know to reset the adjustments for the other factors that play in to the OCI.

The existence of the sensor is a matter of fact. It is described in the BMW tech manuals and other documentation.

[335NJ]

What would be an easy way to confirm the sensor is working properly?

I've put almost 4k on my current oil change, and it hasn't moved at all, I thought by now it would've dropped a hair since the turbo models seems to have blowby, etc.

[derrick603]

Originally Posted by jwzimm

Like I said, it does not only rely on the sensor. If you don';t tell the car that you changed the oil it will not know to reset the adjustments for the other factors that play in to the OCI.

The existence of the sensor is a matter of fact. It is described in the BMW tech manuals and other documentation.

I'm skeptical as to whether or not the sensor actually measures quality. If it did as you say, I'd expect an oil change done without a counter reset would cause the counter to fall at a slower rate since it would be taking the quality of fresh oil into account.

I guess a better test would be to reset the OCI counter without changing the oil. If quality was really being measured, then the counter should fall very quickly.

[Efthreeoh]

Originally Posted by derrick603

I'm skeptical as to whether or not the sensor actually measures quality. If it did as you say, I'd expect an oil change done without a counter reset would cause the counter to fall at a slower rate since it would be taking the quality of fresh oil into account.

I guess a better test would be to reset the OCI counter without changing the oil. If quality was really being measured, then the counter should fall very quickly.

It doesn't work like that. It measures the dielectric constant of the oil. Once the oil dielectric constant reaches a predetermined level that indicates the oil is contaminated, that data, along with several other data, such as time, fuel consumption, engine temperature cycling, rate of change, etc. are used to determine the oil change interval. The oil quality data is not the only data used to determine the oil change interval.

[Efthreeoh]

Originally Posted by derrick603

I'm skeptical as to whether or not the sensor actually measures quality. If it did as you say, I'd expect an oil change done without a counter reset would cause the counter to fall at a slower rate since it would be taking the quality of fresh oil into account.

I guess a better test would be to reset the OCI counter without changing the oil. If quality was really being measured, then the counter should fall very quickly.

Read this...

[krhodes1]

Originally Posted by derrick603

I wonder why this is the case. It sounds to me like the oil level sensor should be pretty simple, it should be able to detect the oil level properly every time it checks (assuming the car is warmed up). Does this mean that if you had a catastrophic oil level failure (something punches a hole in your oil pan, for example, it would take half an hour before car knows something is wrong?

If you put a hole in the pan of a car that only has a dipstick, you will find out in exactly the same way as on our cars - the oil pressure light will come on. The oil level in the sump changes dramatically while the car is in motion, there is no way to have a real time level. It's not different than the gas level gauge - it is very well damped so the needle isn't jumping all over due to the gas sloshing around in the tank. The oil does the same thing in the sump.

[Efthreeoh]

Originally Posted by krhodes1

If you put a hole in the pan of a car that only has a dipstick, you will find out in exactly the same way as on our cars - the oil pressure light will come on. The oil level in the sump changes dramatically while the car is in motion, there is no way to have a real time level. It's not different than the gas level gauge - it is very well damped so the needle isn't jumping all over due to the gas sloshing around in the tank. The oil does the same thing in the sump.

Good analogy. The oil level sensor determines if there is sufficent oil in the sump to allow for engine operation at start up, it's called a static measurement, which you can do anytime on your car when the engine is not running. If there is not suffcient oil in the sump, the system immediately notifies you. And an engine can run a few mintutes without damage with the residual oil on the internal surfaces anyway.