Antifreeze/Coolant is a fluid that prevents the car from overheating or becoming so cold that it won't start. Without it, in the summer, your car would run too hot, and in the winter, your car wouldn't run at all.
Most antifreeze will work in any engine. For diesel engines in general, use a good long life coolant that includes nitrates (red stuff). For regular (green) coolant, most diesel manufactures require...
If it's the original type of coolant it has to be Dexcool approved coolant, which is reddish in color. Most people, including myslef switch to the green color coolant when flushing the cooling...
MOST LIKELY THE ECO FRIENDLY ORANGE OR RED. I HIGHLY RECOMMEND THE OLD STYLE GREEN/YELLOW. YOU WILL NEED TO FLUSH THE COOLING SYSTEM FIRST. THE TWO KINDS ARE OK WHEN MIXED BUT THE NEWER TYPE HAS...