The following link will explain in detail about lot of queries regarding coolant. It clearly explain the potential problem that can cause to an engine with improper coolant. Antifreeze Recycling FAQ Does Fiat sells colant-water mix(not concentrated one) ? ---------- Post added at 07:03 PM ---------- Previous post was at 05:29 PM ---------- A very basic question. How do we know that the engine is over heating or not? Can we trust the engine temperature display. Is there any chance that the display is normal between H and C but engine is overheating? I had this doubt because I never noticed any abnormality in engine temperature meter but the coolant leak that observed can be due to head gasket problem resulted from over heating.