Getting the wrong brake fluid could be disastrous if, by chance, you had an unusual one in your vehicle. Trying to figure out which you should use in your car when there is a shelf full of different types shouldn’t be difficult. So, what kind of brake fluid do I need in my car?
This article is not here to tell you that Volkswagen Golf has DOT4 in it, but it intends to educate you on the different types of brake fluid. By knowing which brake fluid is which, it is relatively easy to determine which fluid is in your vehicle.
What does brake fluid do?
Brake fluid is a hydraulic fluid that applies pressure to moving components in the brake system. There are other components in the brake system, like a brake booster, which make it easier than trying to compress fluid with your foot but to sum it up in a sentence.
When you press the brake pedal, hydraulic pressure is applied to the brake calipers, which squeezes the brake pads against the brake rotors, slowing the vehicle.
Certain brake fluids have another job of keeping components inside the brake system lubricated.
Each brake fluid type explained
Each different brake fluid has its properties and uses for its designed environment. For ease of purpose, the lower the number generally means the lower the fluid’s boiling point.
DOT3 brake fluid is a clear light brown/yellow colored Glycol-based fluid with a dry boiling point of 401 degrees Fahrenheit (205 degrees celcius). Dot 3 is highly corrosive fluid and should be used with care. Because DOT3 is hygroscopic which means it absorbs water from the atmosphere so care should be taken when storing bottles of fluid and its replacement during the service schedules is a must.
In certain parts of the world DOT3 is still very popular but as European car manufacturers used DOT4 on newer vehicles, DOT3 is become less popular.
DOT 4 brake fluid has a dry boiling point of 446 degrees Fahrenheit (230 degrees Celcius). It is a high-performance brake fluid used by nearly all European car manufacturers as standard. It has the same yellowy-brown color as a DOT3 fluid; by eye, it is impossible to tell the difference between the 2. It is also a glycol-based fluid that acts as a good lubricant for components in the brake system, such as the ABS pump.
DOT 5 brake fluid has a dry point of 500 degrees Fahrenheit (260 degrees Celcius). It is a purple-colored silicon-based brake fluid. It is not a good lubricant, so it cannot be used on road vehicles with ABS systems. DOT 5 brake fluid is not hygroscopic, so it does not absorb moisture, which means brake systems with DOT 5 typically have a soft brake pedal. You can also get localized water puddles in the brake fluid, which attracts rust to metal components, even though the liquid is not corrosive.
You would typically find DOT5 brake fluid in military, race cars, and motorbikes. All those where brake fade is a possibility; as you might have guessed, it is an expensive fluid.
DOT5.1 has a dry boiling point of 518 degrees Fahrenheit (270 degrees Celcius). It is a yellowy-brown glycol-based fluid almost identical to DOT3 and DOT4 fluids. It is used on high-performance road cars, supercars, and race vehicles for its very wet high-boiling point. Similar to DOT5 brake fluid, it is costly to purchase and needs to be replaced during service schedules.
LHM or Liquide Hydraulique Minerale is a very unusual brake fluid unique to Citroen, Peugeots, Rolls-Royce, and Bentleys. It is a green mineral-oil-based hydraulic fluid for the brake system, power steering, and hydraulic suspension. LHM has a dry boiling point of 464 degrees Fahrenheit (240 degrees Celcius).
Not all Citroens, Peugeots, Bentleys, or Rolls-Royce’s come with LHM as standard; the ones that do will have a self-levelling suspension system. It’s usually easy to tell by the green-colored components in the engine bay.
Can I use any brake fluid for my car?
You shouldn’t just put any old brake fluid in your car and should check the handbook for guidance. Brake fluid has the essential job of lubricating the ABS pumps, so the manufacturers design the braking system and its components with a specific type of brake fluid.
Another way to tell which brake fluid is used is to look at the filler cap for the brake fluid. It is usually black or yellow (unless LHM fluid is used) and will sometimes have the type of brake fluid printed on it.
Can you mix different brake fluids?
If your vehicle has BF DOT 3,4, or 5.1, then the brake fluid can be mixed without causing any damage to the brake system; However, you would only go up the scale, and you would only do this in an emergency. For example, if your vehicle has DOT 3, you put either 4 or 5.1, but if your car has DOT4, you won’t put DOT 3 in it. You would only use DOT 5.1. The only reason you can mix these is that they Glycol-based. If you did have to do this, it should only be a temporary solution because each fluid has its unique boiling point. Replace mixed brake fluid at the earliest convenience, which is done by carrying out a full brake fluid flush.
DOT5 is strictly for DOT5 braking systems only. DOT5 is silicone based, so it cannot be mixed with Glycol-based fluids.
Vehicles with LHM fluid is mineral based and can only be used with LHM fluid vehicles. Regular DOT 3,4,5,5.1 fluids do not have the same properties, so they cannot be mixed.
Ensuring your brake system is in top condition starts with ensuring your vehicle has the correct brake fluid. When answering what kind of brake fluid I need in my car, essentially, if your vehicle has a yellow/brown colored liquid, it is safe to mix with DOT3, 4, or 5.1. Especially if the fluid is low, Mixing LHM or DOT 5 brake fluid with other types of brake fluid cannot and should not be done. If you think your vehicle has either of these fluids, it would be wise to have a mechanic or the OEM vehicle manufacturer confirm this to know if you ever get caught in a problem.