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The difference between dot 3 vs dot 4 brake fluid

October 26, 2017 | Quick Service Info

Brake fluid is something that all vehicles have. It doesn’t matter if you’re driving a motorcycle, truck, or an economy car. The job of brake fluid is to move the crucial components of your braking system which are responsible for slowing down your vehicle when you press on the brake pedal. Basically, the fluid causes the pistons in the braking system to compress the rotors so that your vehicle is able to slow down.

Brake fluid is always subjected to a fair amount of heat. However, there is only so much heat it can take before it starts to boil. Once this happens, the fluid will form air bubbles which will make it compressible. Brake fluid is not supposed to be compressible. Therefore, if you have brake fluid with air bubbles in it, then pressing down on the brake pedal will cause this air to compress while the vehicle has trouble slowing down. If the brake fluid is very overheated, then the vehicle won’t respond at all to the brake pedal being pressed.

Top 4 Differences

There are two different types of brake fluid that are used by most auto manufacturers. There is dot 3 brake fluid and dot 4 brake fluid. Below are the top 4 differences between the two types of fluid.

  1. Boiling Point – Dot 4 brake fluid has a higher boiling point than dot 3 brake fluid. If you tend to do a lot of heavy braking with your vehicle, then dot 3 brake fluid could easily boil. Dot 4 brake fluid is more reliable when you’re regularly doing a lot of heavy braking because it doesn’t boil as easily.
  2. Chemical Components – Dot 3 brake fluid is made from ether and polyalkyelen glycol being mixed together. This mixture creates a brake fluid that can handle wet conditions and average heated conditions. Dot 4 brake fluid is made of borate and glycol. This mixture makes the brake fluid more stable and able to handle higher temperatures.
  3. Car Types – The average economy car will use dot 3 braking fluid because the driver won’t perform aggressive braking that frequently. However, you can expect to see dot 4 braking fluid in police cars, motorcycles, and racing cars; since they all brake more frequently and aggressively.
  4. Boiling Capacity – Dot 3 braking fluid contains both a great wet boiling capacity and dry boiling capacity. This means the fluid will work well when it’s exposed to water and the open air. Dot 4 braking fluid is best when it comes to a dry boiling capacity. Unfortunately, its wet boiling capacity is not so great.

Read also: What Happens if you Put Gasoline in a Diesel Engine

Changing Brake Fluid

A lot of people don’t think that they need to change their brake fluid levels. Sometimes the fluid level drops when you have worn brake pads. Your braking system will have marks which read “FULL” and “ADD.” If the brake fluid level floats around “ADD,” then it means you need to flush your braking fluid and then replace it with new braking fluid. The filler cap will indicate whether the manufacturer recommends dot 3 brake fluid or dot 4 brake fluid. You can also find this information in your owner’s manual.

If you realized that you put the wrong brake fluid in your vehicle, the first thing you should do is take the vehicle to the nearest auto body shop and have them drain it for you. Not only that, you’ll want the mechanic to run a diagnostic check on your braking system to see if any of the components were damaged from the wrong braking fluid being used. Even though your brakes may have felt like they worked on the way there, it doesn’t mean they will keep on working over the next several days or weeks. That is why you need to change the brake fluid right away to avoid any problems that could happen.

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