How do you REALLY ever know the oil level?

[Dackelone]

Originally Posted by Rob_BMW_PNW

The oil sensor is also a oil quality sensor too, which it can read lower levels if it is getting too 'bad' of quality

Originally Posted by The Wind Breezes

Can anyone back this up because as far as I know the car just estimates when you need to do an oil change and the estimation has nothing to do with actually measuring the quality of the oil.

Rob_BMW_PNW is correct about the oil condition sensor. Here is a pdf on the OCS and how it works.

Btw... when ever I change my engine oil - I always notice that the oil level shows in the middle of the range. It will not show "full" until I drive the car for a while. Also... the more short trips you do... the more diluted your engine oil becomes with gasoline. You need to drive the car a LONG time, before the oil level will show a correct oil level. I have noticed that say I am driving the car for 20 minutes... the oil level can read middle or low on the scale... but IF I drive for one hour on a long trip(without adding any oil) the oil level will go up to "full". I never trust that gauge - until I have been driving the car for at least 45 minutes on the highway/Autobahn.

This is one reason to change your engine oil more frequently. I have also noticed that IF I go more than 6K kms between oil changes... or IF I drive the car very hard... the engine will use some oil. BMW says one liter per 1K kms(600 miles is normal). For me its more like one liter in 6K kms - IF I am driving very hard. Driving normally - I don't use any oil between my 6K to 8K kms oil changes.

Also... some early '08 cars had an issue with the oil level reading low. BMW updated those cars via a SW update. Also early OCS can go bad. Our cars are getting old.. so its entirely possible your OCS could be bad. OP perhaps that is why your car has a stored code. ?

[houtan]

Originally Posted by Rob_BMW_PNW

http://www.e90post.com/forums/showpo...79&postcount=5

All I got on it.

Woah. I had no idea. Thanks

[dh58]

It's off... Especially if you have a bigger oil cooler etc..

I had no issues.. always said I was in mid range and I park on flat surfaces.. Checked very regularly (once a week)..

When I got the oil drained, only 4L came out... I get my oil changed every 5k.

I really wish I knew the answer, but i'm chiming in on my experience..

The sensor isn't always right..

[The Wind Breezes]

Originally Posted by Rob_BMW_PNW

http://www.e90post.com/forums/showpo...79&postcount=5

All I got on it.

The sensor is capacitative with two capacitors one inside the other, the inner one measures the quality of the oil the outer one measures the oil level. The inner one is always full of oil so the only variable will be dielectric quality while the outer capacitance is mostly determined by how much oil there is in there (as opposed to air or whatever...oil is a much better dielectric).

The oil doesn't function as a resistor but as a dielectric.

https://en.wikipedia.org/wiki/Dielectric
https://en.wikipedia.org/wiki/Capacitor

[juld0zer]

Last time i changed the oil, i drained 6.8L with the car level on a hoist.
8000km change interval, and i did the last oil change with 6.5L oil.
Fuel dilution? I drive at least 15km each time i start the engine and the oil temp always gets up to operating temp

[bNks334]

Originally Posted by juld0zer

Last time i changed the oil, i drained 6.8L with the car level on a hoist.
8000km change interval, and i did the last oil change with 6.5L oil.
Fuel dilution? I drive at least 15km each time i start the engine and the oil temp always gets up to operating temp

Send in a sample to blackstone... no one on the Internet can help you draw that conclusion lol

There is more oil in the car than what gets drained during an oil change. .3 liters difference could be a million different variables.

[dman928]

Originally Posted by iminhell1

A good argument is the simplest one, the car must be running.


from the owners manual:

"Your car is equipped with an electronic oil-level monitor.
For precise measurement and display of the oil level, the engine must be at operating temperature, i.e. following at least 6.2 miles/10 km of uninterrupted driving. You can have the oil level displayed while you are driving, or while the vehicle is at a standstill on a level surface and the engine is running."


With a traditional dipstick you can check oil level prior to engine start and you also don't need to bring it up to operating temp.
IMO, that can potentially save 6.2 miles of bearing damage from low/no oil.

Ding ding ding.