After looking at my transmission oil level on my 83 sd (i'm guessing about 1L missing ) i decided that it might be a good idea to change it
Looking for oil i saw that the original ATF oil is about 11$ to 13$ per litre.
I find it a bit $$
Manual says that i need around 7.5 ( if my memory is good)
I used the search fonction and i read something about Mobil synthetique ATF oil
My car has 414k km.

I have a small dilema
Should i change all the fluid with the synthetique Mobil and the filter ?
should i just fille up the missing oil ?
Should i go MB all the way ?

Any input is welcome
btw i don't wanna start a long oil tread/war :p