which coolant to use???

[Dr HMS Derv Destroyer]

recently noticed a grey like sludge in my header tank, non of the gaskets have gone and no mayo on the oil cap.

now i have been told if i have mixed mineral coolant with someother type coolant, that this can happen.
this was only noticed after i had a leak, fixed that and topped up the system with halfrauds pinky/orange readymix coolant.

so what do i do? full coolant flush and then what specific type coolant do i use? engine is a k9k dCi 80

 

[MartinR]

Full coolant flush,then put renault type-d coolant in

 

[Dr HMS Derv Destroyer]

Ok cheers