Mixing different brands of coolant is not recommended, as coolants from various brands may contain different chemical formulations, additives, and base fluids. When mixed, they can potentially react with each other, reducing their effectiveness in protecting the engine and cooling system. This could lead to corrosion, overheating, or damage to vital engine components. If you must top up your cooler with a different brand, ensure that the new cooler is compatible with the existing one. It’s essential to check the coolant’s specifications, such as its type (ethylene glycol or propylene glycol) and its color, as these can indicate compatibility. For optimal performance and safety, it’s best to use the same brand and type of coolant throughout the lifespan of your vehicle, or flush the cooling system thoroughly before switching brands. Always refer to the vehicle’s manual for the manufacturer’s recommended coolant to ensure the best protection for your engine.