Colorless fluid – Antifreeze is typically died a color, if the fluid in your coolant reservoir is clear, rusty colored, or has things floating around have your coolant system flushed immediately.
Oily Fluid – If the fluid in your coolant reservoir has signs of oil or looks sludgy it could indicate a head gasket failure and requires immediate attention.
An antifreeze is an additive which lowers the freezing point of a water-based liquid and increases its boiling point. An antifreeze mixture is used to achieve freezing-point depression for cold environments and also achieves boiling-point elevation (“anti-boil”) to allow higher coolant temperature. Freezing and boiling points are colligative properties of a solution, which depend on the concentration of the dissolved substance.