six month ago i changed coolant, it was 6 years old, 80000 kms, put Total purple EVO PLUS concentrate with deminiralized water 50:50, no air bubbles, overheating on such, it works normally, but after that i noticed small drops in expansion tank, in 1 month, 1000 kms the level drops by 1 mm, that is about 0.1 liter, from min to max is probably 1 liter, so in 12 months maybe it can be maximum one liter, but i think no, i didnt put 0,6 litres in 6 months. more likely 0.3l. i am using Total for long years because is quallity and not expensive.

1 month ago i put new tank cap Febi, but all same, it is not much, i add 0,2-0,3 litre in 2 months.

also on cap on inner side is always drop of fluid, (old and new one) and thats normal i had it on all cars i had in life i try it with tongue, and its only water. on previous cars also condensation happened and was always tasted like coolant (strong sugar taste) now i have only water condensate. it is possible that only water condeses and evaporates, and coolant stays for ever reasons. i dont get it..

https://lubricants.catalog.totalenergies.com/catalogue-B2B-fr/fr_FR/y61_glacelf-plus-evo

If the expansion vessel is correctly sealed, there should be no (or negligible) evaporation from what is a closed system.

Yes, the H2O content of the coolant will boil-off sooner than additives, but should not be lost from the system.

I'd suggest checking that the cooling system is actually pressurising (and holding pressure) when it heats up.

Small point. As long as any drop from MAX then stays as is and is not at MIN then good. There are no FILL TO THIS LINE. markings. Many vehicles set the level. Many get serviced and filled to MAX, you get home and the coolant level is back where it was before the top up.