On a W221 MY06 with M272 engine I have from time to time the Mixture adaptation on the right bank beyond limits.
After erasing, all the actual data is OK.
This is happened again and again 2 or 3 days after erasing the fault till I upgraded the engine software.
Now the fault code is coming back after 2 weeks of driving.
I use only Eur5 gasoline with octane 100.

Car has only 32K km at her age and I am thinking to change the fuel filter.
Any advice should be appreciated!