When the engine overheats when AC is not in use but overheating stops when AC is turned ON, there is likely a problem with the cooling fan system. Either one out of two fans is not working or the only fan is not working optimally.
As brake pads wear down, the level of brake oil in the reservoir wear down. Some wrongly react to this by topping the brake fluid to compensate for the level drop. Brake oil should be topped during pads change.
The cooling system is a key system of automobiles that controls the temperature of the engine and transmission. Modifying it can cause undesirable consequences on fuel economy, longevity, safety and so on of vehicle parts.
The eCVT in hybrid cars have electric motor/generator sets in it which the engine and regenerative brake system uses to charge the hybrid battery. A wrong transmission fluid in it will cause short circuit, malfunction and damage.