not sure bout using them in older cars don't see a problem. i think iam going to switch to the chrysler hoat (pink) antifreeze in my 79 truck. do not mix pink and green and do not use dexcool use the chrysler hoat coolant it is much better and is not the same as dexcool. i work in a gm and chrysler dealer and have seen way more cooling system problems with dexcool that the hoat. with corrosion and it gets kind of waxy in areas that don't have a high volume of flow. pretty much dexcool is junk. have not seen those problems with chrysler 5 year antifreeze.