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No Oil Dip-stick with new car engine.. How does it know?

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Cunning Plan:
I was playing with a new Mini (not mine), F55 1.5d to be exact and there is no oil dip-stick, instead you have to use the on-board computer to run an oil check, which then displays the results on the centre console screen, similar to this one, but imagine an image of a dipstick with a level indicated on it:



That bit is quite simple, you would think a sensor just detects how much oil there is and displays it on the screen, however, to measure the oil, you have to have the car running and in neutral, which then prompts the system to start checking the oil.

On older engines, I have always waited for the car to cool and the oil to return to the sump to get an accurate measurement of exactly how much oil is in the sump and therefore, available to the engine. My understanding is, if the engine is running or has just been run, the oil will be distributed around the engine, in the journals, head, passageways, turbo etc, so the amount in the actual sump will appear to be lower.

So, how do new engines, without dip-sticks measure oil?  

Big Mouse:
I suspect its measuring pressure rather than amount. Fluctuation in the pressure would indicate a leak therefore it needs oil. That raises the question of how do you know when you've fed it the right amount of oil? the only way is to drain it, fit a new filter and top up with the recommend amount of oil.

Oil level problems with new (2007+) minis is well covered on the interweb

Roadkill:
It might have a level sensor - like in a fuel tank ?

And, in fairness, oil level with the motor NOT running is kinda pointless . . . You could put 10 litres of oil in the engine but, if when running, it only is using 1 litre, then the other 9 litres is extra weight and drag on the motor (within reason).

Cunning Plan:
Quoting: Big MouseI suspect its measuring pressure rather than amount. Fluctuation in the pressure would indicate a leak therefore it needs oil.

That makes sense.

So do you think it is drawing oil through a 'device' which expects X amount of oil to pass through in X time, if it is less by pressure, then you have less oil?

I will take a picture of the dash display when it has completed the check, it seems to know exactly the amount of oil in the system. It even shows a dip-stick with a level on it, so the oil can be somewhere between the minimum and maximum mark.

Quoting: Big MouseThat raises the question of how do you know when you've fed it the right amount of oil? the only way is to drain it, fit a new filter and top up with the recommend amount of oil.

For oil changes, I guess it would be the same as any other car in that you would already know the amount of oil to put in by looking at technical specifications.

I *think* for top-ups, the computer display will tell you how much to put back in. Total guess at the moment though as the car is at maximum level.

Quoting: RoadkillIt might have a level sensor - like in a fuel tank ?

That would work if the engine is 'off', otherwise the oil would be fluctuating with every movement of the crank, right?

Quoting: RoadkillAnd, in fairness, oil level with the motor NOT running is kinda pointless . . . You could put 10 litres of oil in the engine but, if when running, it only is using 1 litre, then the other 9 litres is extra weight and drag on the motor (within reason).


I understand what you are saying, that the engine will only use X amount at any given time. However, the oil is not just for lubrication, it is also for cooling, so my understanding is, if we pretend that the oil is a solid cube, once one cube has gone around the system, the next cube is cooler in the sump waiting to go around next.

With that in mind, the engine has been specified to need, for example, 6 litres of oil as the engineers have worked out that 2 litres are required to go around the engine at any one time, 1 litre is in the filter being cleaned and 3 litres are in the sump cooling and providing lubricant to the bottom of the crank.

art b:
I prefer to pull my dipstick out..

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