Dot 3 Vs. Dot 4 Brake Fluid

Newton's first law dictates, "Every object in the state of uniform motion will remain in that state of motion unless an external force acts on it." In other words, your car won’t stop unless your brakes work or you get into an accident. We’d prefer you to choose the former method.

However, to have functional brakes, you need to be using the right braking fluid. Many argue between Dot 3 vs. Dot 4 brake fluid, but people miss out on the fact that different braking fluids are essential for different situations. We're here to help set the records straight.

Why We Use Brake Fluid?


Before we get into the difference between Dot 3 and Dot 4, it's essential to understand why braking fluid is so critical. Braking fluid is simply hydraulic fluid, which is stored in the brake lines.

When we apply the brakes, the force produces pressure in the brake lines. This, in turn, cause the fluid to evenly provide strength to each rotor located at the corner of the vehicle. The rotor then provides force to the brake pads, which in turn creates friction in the drum, thus bringing the car to a stop.

Dot 3 vs Dot 4 Brake Fluid – Differences in between


If you have a look at your brake oil cap, you’ll notice the company mentions to use Dot 3 or Dot 4 brake oil.


Both are available at quite different prices and are necessary for specific situations. These differences are discussed below to help you choose one that fits into your requirements.

Targeted Type of Driving and Car

We've mentioned both these points together as they are in correlation with each other. Braking the fluid is strongly intertwined with how you use your vehicle.

If you're someone who likes to drive rough, you'll also be involved in rigorous forms of braking. This will require precision braking because of a split-second, and the difference here could become the difference between life and death. Thus, for you, Dot 4 fluid would be perfect, given its high boiling point.

On the other hand, Dot 3 users are mainly targeted as regular drivers. These people drive their cars regularly, such as for commuting. For them, harsh braking isn't entirely necessary, and Dot 3 fluid should do just fine.

Dot 3 users are the main drivers of regular road cars, such as sedans and hatchbacks. On the contrary, Dot 4 is what is used mainly in police vehicles, sports cars, and SUVs.

Varying Boiling Points

The boiling point is one of the most noticeable differences that make Dot 3 and Dot 4 comparable. As we've learned in 6th-grade physics, when you heat any material solid, liquid, or gas, it tends to expand.

In an environment that is close to your engine bay, things are supposedly getting very hot. And if your braking fluid easily expands, it could be a cause of concern.
Dot 3 fluid has a lower boiling point than Dot 4, giving Dot 4 the upper hand in this case. The lower boiling point means the liquid is highly likely to absorb water.

This is also known as the wet boiling point and occurs during regular driving when you take off the reservoir cap. These can cause damaging effects to your braking system over long periods.

Boiling Capacity

The boiling capacity of fluid indicates how well it'll work with a different medium. Since, you cannot eliminate the chance of the brake fluid being compromised.

Dot 3 is compatible to work with both water and air, as its composition is not as sensitive to these foreign elements.

However, even though Dot 4 works quite effectively with air, the same cannot be claimed for its wet boiling capacity. The performance you’ll be getting comparatively would be worse than in ideal conditions.

Chemical Structure

Another point of difference possessed by the two-fluid is their chemical makeup. Dot 3 braking fluid is based on diethylene glycol (DEG) structure. This helps the braking fluid hold up in heat, dry, and wet conditions. Making it great for an everyday driving companion.

Dot 4, on the other hand, is made up of a glycol and borate ester structure. The borate ester helps the fluid deal with higher temperatures and makes it highly resistant to water. This means that it won’t allow your metal components present in your brakes to be corroded.

The Difference between DOT 3 and DOT 4 Brake Fluids

Conclusion

In this battle of Dot 3 vs. Dot 4 brake fluid, it's no surprise that there are no winners. Both fluids, even though performing the same task, are designed to serve different individuals.

If you're the type whose drifting skills are famous in the streets, then Dot 4 is right for you. And if you're just trying to get to work, then Dot 3 should do you fine.

John
 

John D. Archer is a mechanical engineer and writer based on the area of automotive accessories at brakeshub.com, A resident expert and professional, John is passionate about all things automotive and loves to share his knowledge. He has good experience in all kind of automotive accessories. He has worked as a chief mechanical engineer in some reputed automotive garage firm.

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