Originally Posted by cn90

Have been using Green Prestone coolant (the concentrated type $12/gallon at Target etc.) + mixed with distilled H2O for 25 yrs in different BMWs.

Zero issues.

You should look at the coolant passage of my cars after 20 years of Green Prestone, it is pristine clear. Just look at the photos in the DIYs I wrote on bimmerfest.

No need to buy BMW coolant.