So I checked my oil today because I smelled some burning but it says I'm a little low but I don't understand why I don't get no warning lights on my xfr something that tells you that you're critically low shouldn't I get some kind of warning I guess I should just change the oil but I don't even know if I have a leak or not because I have that engine cover underneath how do we know what's going on with this car

 

You should get an Amber warning in the message center if your oil level is down by 1litre (1.8 pints),a Red warning if your oil level is below the safe operating level(down by 1.5litres or more)
This information is provided in the Owners Manual (around p199 ). If you do not have an Owners Manual you can download one from above Sticky Threads. I would recommend you read it.

 

These warnings are listed in a manual, but... These are disabled in a factory engine tune, so these never pops up (both amber warning and red warning would pop up when there's 0L of oil in engine, which never would happen).

 

What exactly is a " factory engine tune" and why would any rational person( or factory) disable a safety warning ?

 

It's the stock (factory) software in the ECM (engine control module).
The reason is exactly a same as for a dampened temp gauge on the other models (which would sit in the middle of the gauge while coolat temp is 65 to 110 degC, then jump to the red zone) - "not to bother a customer".
Here's an example from a X351 Denso, 5.0 SC. XF, XK, RR, RRS, D4 with the Denso ECM's - these are all a same and the values in a stock tune are exactly a same.

 

Presumably those values are used when the engine is running. You can only get an oil level measurement when the engine has been shutdown for a while, say 10 min or so. Similarly when I extract dirty oil from my 2012 XF I can check the function of the oil level sensor display on the instrument panel and it behaves as stated the manual.

 

IF you're checking oil while draining it, its a diferent scenario.
Yes, these are popping up even on a running engine too, since the sensor is working while engine running too and the oil level/volume available through the OBD while engine is running.
Sure, the offset is needed (like the yellow warning should be triggered not on 7l, which is 1l low, but at 5.5l), but otherwise these functions working just perfect, saving an engine (if the values are modified).