Rotax 912 oil level idiosyncrasy

Have you noticed this significant difference between cold and warm engine?
(This is after gurgling the engine):
Cold Engine: the oil level is at the middle of the flat of the oil dipstick
Warm Engine: the oil level is at the top of the flat of the oil dipstick

As far as I checked I did not find any warning about this peculiarity in Rotax manuals (operator and Light Maintenance).
If you are not informed of this fact you are at risk of overfilling the oil tank in a cold engine. This may also explain why you got oil spread over the belly of your plane.

It is caused by the viscosity of the oil being a higher when it is cold.
If there is some oil in the engine when you do the burp process, it is coating a large surface area of the engine case and when cold does not easily flow out the small drain port on the bottom.
Getting a good oil level check when the temperature is very cold is difficult unless you do the process a number of times. A better process is to do an oil level check when the oil is warm after shutdown.

Good to know

I began doing the burp and oil check shortly after a flight on the premise it was easier and quicker with the engine warm. And it was but the levels were at least a little different, Lower cold and higher warm. Thanks for the explanation.

Scott's answer makes perfect sense but still the difference between hot and warm goes beyond what I expected. I believe this fact should appear somewhere in the Rotax 912 operator's manual.This reinforces the incentive to check the oil level after flight as mentioned by Patrick and as counter-intuitive as it may be (although it might not work well for a multi-operator RV-12).

We found early on when working with the Rotax (pre RV-12) that the best time to gurgle the oil to check the level was immediately post flight.

The system (pressurising the crankcase to scavenge the oil back to the tank) is much more efficient when hot.

If when doing the pre-flight the oil level is on the dipstick flat then you're good to go even if it has dropped since the 'hot' check (unless there's a load of oil under the nose....).

On my Rotax maintenance course, I was told that the relative position (height-wise) of the tank to the crankcase on different airframe/engine installations does make a difference to the amount of oil level change between hot and cold. Apparently some oil can bleed back into the crankcase over a period of time.