"I've read somewhere that there different kinds. Cheaper ones I think have ethynol and better ones are propylene glycol I think ?"
I think maybe you are confusing comments about RV (fresh water) anti freeze with engine coolant anti freeze. The above applies to the RV type - pink stuff - thats potable water system safe.
For engine coolant its important to use the same stuff to top off as mixing coolants generally NOT recommended. You need to figure out what kind of diesel AF was used.
Don't be tempted to use any auto parts store stuff that claims " safe to use with any other coolants".
NAPA can generally get anything you need overnight once you figure out what it is.
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