Coolant use and Cooling System for Subaru WRX/STi

What is the best coolant? The “best” coolant differs from stock SOA advice, so use at your own discretion. Ensure you choose one that contains no silicates and no phosphates. Silicates act as a cleaner, but also eat away at water pumps and seals. If you mix a coolant containing phosphates and water with a high mineral content, the phosphates in the coolant may “drop out” and form deposits in your cooling system that can lead to corrosion. Only recently have aftermarket coolant manufacturers started producing silicate and phosphate free coolant. Generally speaking, the types of coolant that are compliant are the newer “extended life” coolants. However, you should carefully review the product labels and/or product websites to ensure they are silicate/phosphate free.

What is the best coolant ver 2.0? As far as the best coolant for removing heat from your engine, it would be 100% water. You might even see better heat removal capability if there is a coolant additive mixed with it. Obviously, 100% water should be used in racing only applications and only by advanced users. Its use in a normal passenger car is NOT recommended even for short use. Water has a very high heat capacity. The reason it is mixed with ethylene or propylene glycol is to lower the freezing point below 32F and raise the boiling point above 212F. Both water and ethylene or propylene glycol are essential to the coolant’s function.