Hello Paul, I drive a 2004 VW Touareg, which requires DOT3 brake fluid. When I recently visited a nearby petrol station, they only had DOT4 brake fluid available. What is the difference between the two, and can I use DOT4 in place of DOT3? Mugisha
Hello Mugisha, yes, you can use DOT4 brake fluid instead of DOT3 in your VW Touareg, but not the other way around. DOT4 is an improved formulation with a higher boiling point and better performance in high-temperature conditions, making it suitable for newer vehicles equipped with Anti-lock Braking System (ABS) and traction control.
To understand the distinction, consider brake fluid as the lifeblood of your braking system. It builds hydraulic pressure to activate the brakes while also cooling the system to prevent damage to seals and pistons. As brakes function by converting kinetic energy into heat, excessive heat can cause the brake fluid to boil, leading to air pockets in the system and a reduction in braking efficiency.
The key differences between DOT3 and DOT4 brake fluids are:
Boiling point: DOT4 has a higher boiling point than DOT3, making it more resistant to overheating in demanding driving conditions.
Composition: DOT3 is composed of ether and glycol, while DOT4 contains borate and glycol, giving it better moisture control and corrosion inhibition.
Performance: DOT4 is designed to handle higher temperatures and braking pressures, which is why it's preferred for modern high-speed vehicles with advanced braking systems.
If you are switching from DOT3 to DOT4, it is advisable to completely flush the old brake fluid from the system using a professional brake fluid bleeding tool.
