DOT3 VS DOT5 – What’s the Difference Between DOT3 and DOT5 Brake

Brakes are probably the most neglected maintenance component in your car ride despite knowing its importance to drive safely. If you religiously change your engine oil for a swift drive, why not change the brake fluid too to keep those brake shoes in proper shape?

While it might sound easy to fetch a bottle of fluid brake from the market, you need to have a thorough knowledge of different types of them. For instance, you should know what’s the difference between DOT3 and DOT5 brake fluid or DOT4 and DOT5.

Unfortunately, just Googling those terms won’t help as you would only learn their definitions. To understand the purpose of each fluid brake and the key difference between their various types, you must go through a complete guide. Therefore, we have decided to take that matter into our hands. Here you will learn everything about brake fluids as well as the difference between DOT3 and DOT5 brake fluids.

What is Brake Fluid?

Before taking a deep dive into the different types of brake fluids, first, we need to learn what brake fluid is and how it works. A vehicle’s braking system rapidly converts kinetic energy into heat in order to reduce the car’s momentum. In today’s world, brake fluids are used to build up the pressure a braking system requires to make those brake pads and rotors work. 

Brake fluid is a flowy, low viscose hydraulic liquid that transmits the kinetic force from the brake pedal to its caliper, which then rubs against the rotor to decrease the vehicle’s momentum.

Why is Brake Fluid Important?

Firstly, it is important for perfect braking performance, in fact, having the right braking fluid for your car would minimize the risk of accidents (Learn in detail here why your car shakes when braking). Failure to get the correct braking fluid can cause a longer braking distance and ultimately lead to brake failure.

Like engine oils, different types of brake fluid come for the braking system’s maintenance. They are labeled and categorized based on their DOT ratings. For those who don’t know, DOT stands for Department of Transportation.  It is an agency responsible for ‘planning and coordinating federal transportation projects.’ Moreover, it lays down safety guidelines for all major transportation modes.

A DOT rating represents that the product has met or exceeded the Federal Motor Carrier Safety Administration’s (FMCSA) safety fitness standards. A DOT rating can be broken down into 3 properties; boiling point, chemical substance and moisture control over time.

Types of Brake Fluids

Typically, three types of brake fluids are available in the market; DOT3, DOT4 and DOT5. If you are new to driving, you must be thinking about what these numbers suggest? DOT3 represents the basic type of brake fluid, while DOT5 is considered the premium one. DOT4 has recently started gaining popularity and is being used in regular vehicles. Before that, DOT3 saved the spot.

Let’s learn about each in detail.

  • DOT3 Brake Fluid

Like we said earlier, DOT3 is the basic one. The quality of the brake fluid improves as the number ascends. It comprises 80% Glycol and 20% other substances. It comes in blue color. The boiling point for different DOT3 brake system fluids varies from brand to brand. However, generally, they have 140 degrees Celsius wet boiling point and 205 degrees Celsius dry boiling point. The wet boiling point is taken into account when the brake fluid has trapped moisture with time. Though, it gains less moisture than DOT4 fluid.

  • DOT4 Brake Fluid

DOT4 has recently got popular due to its outstanding properties. It is being more commonly used as it closes the gap between DOT3 and DOT5. It boasts the properties of both and comes at affordable prices. This is one of the reasons why it is popular across the US. If we talk about its composition, it comprises 50-65% Glycol ether base and 20-40% Borate Ester base. Its wet boiling point is 170 degrees Celsius and 270 degrees Celsius dry boiling point. Although its boiling point is higher than DOT3, it gains moisture quicker. Indeed, it’s a reliable brake fluid and also a perfect fit for your vehicle if you are up for quick fluid changes.

  • DOT5 Brake Fluid

DOT5 is a high-end brake fluid used in most vehicles made for high-intensity conditions. Since it comprises silicone, it is less likely to contain moisture with time. With 180 degrees Celsius wet and 260 degrees Celsius dry boiling point, the fluid offers more compressibility and reliability than the other two types. If you wish to achieve stupendous braking performance and have a flexible budget, you should definitely go for DOT5.

That said, some DOT4 brands are also offering fully synthetic brake fluids with higher boiling points than DOT5.

What’s the Difference Between DOT3 and DOT5 Brake Fluid?

Over time, brake fluids OEMs have exhibited massive improvements and raised the competing bars. While there are no clear-cut predetermined metrics for brake fluids, they can be differentiated based on some general differences. In the following, check out some common differences between DOT3 and DOT5 brake fluid.

Options

DOT3 brake fluid

DOT5 brake fluid

Boiling Point

Dry: 401 F/205 C

Wet: 284 F/140 C

Dry: 500 F/260 C

Wet: 356 F/180 C

Chemical composition

It comprises ether and Polyalkylene glycol

It is made of blended hydrophobic

Polydimethylsiloxane and Tributyl phosphate.

Boiling capacity

Its dry and wet boiling capacity is better than DOT4

It has the best dry and wet boiling capacity

Color

New ones are bluish in color

It is purple in color

Meet standard requirements of

FMVSS 116,

SAE J1703

ISO 4925 Class 3

FMVSS 116,

SAE J 1705

ISO 4925, Class 5

Price

$13 to $16.

$18 and $45.

Which Brake Fluid is Best for your Car?

Go through the owner’s manual to determine which brake fluid is best for your car model. Usually, it suggests the brake fluid type you should use. If it tells you to use DOT4 then first drain the old brake fluid out of the brake lines before pouring the new one.

Lastly, remember that brake fluid has a short life. Always use a fresh one and never use the old one if you are servicing your braking system yourself.

Conclusion

Brake fluid is mandatory for almost every type of vehicle. However, it does not matter if you are driving an economy car, motorcycle or a truck. The work of the brake fluid is focused on moving the vital components of the braking system conveniently. The use of brake fluid also enables the pistons to compress the rotors on the braking system so that the car speed can be slowed down. Lastly, remember that brake fluid has a short life. Always use a fresh one and never use the old one if you are servicing your braking system yourself.

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