Paskman
Not a user
If you are going to be picky about it, it should be Citroën - although I have just noticed that the Citroën website does not seem to use it,
The two dots over the e mean that the oe is not dipthongised, so the o and the e are pronounced separately if one is being ultra precise. A French peron would pronounce it (slightly exaggerated) "citrowhen".
There is a name for the two dots, but I can't remember what it is. It is not an umlaut.
And don't argue. I've got a degree in modern languages.
Was the degree from the University of Buenos Aires?