Dot 3 and Dot 4 Brake fluids are recommended by most vehicle manufacturers and are a glycol based fluid that has similar characteristics to antifreeze. The Dot 5 Brake fluid is a silicone based fluid that is not compatible with many OE brake systems. You need to make sure you refer to the Volkswagen manufacturer’s recommendations when adding or flushing brake fluid. Today’s Volkswagen's have very complex brake systems and most on the road today have ABS systems that are very sensitive to the types of fluid used in the Cabrio braking system. Adding the incorrect type of fluid could cost you thousands in Volkswagen Cabrio brake system repairs.
The Volkswagen Cabrio cooling system is made of aluminum components and requires a Phosphate free coolant. DO NOT PUT an over the counter antifreeze in your Volkswagen Cabrio, as it will ruin the radiator and water pump.