which is the correct brake fluid to use for cmax 1.8tdci 2005 ........ i thought it was Dot4 But i recently purchased some online from a ford dealership . On supplying my reg they informed me that i required super dot 4 and not Dot4. I can find nothing in owners manual and also on filler cap it has dot 4 .....so i am a little mistified to which is correct and if either is ok or can be mixed?

So if anyone can enlighten me to which is the correct brake fluid it would be much appreciated