If you’ve ever opened your vehicle’s hood to check the brake fluid reservoir and noticed it was time for a top-up, you might have asked yourself: “Should I use DOT 3, DOT 4, or DOT 5 brake fluid?” คุณไม่ได้อยู่คนเดียว. Choosing the correct brake fluid is more than just picking a number off the shelf—it directly affects your vehicle’s safety, performance, and longevity.
In this blog, I’ll break down everything you need to know about these brake fluids from a real-world driver’s perspective. Whether you’re a DIY mechanic or a curious car owner, this guide will answer all your questions.
ทำความเข้าใจพื้นฐาน: What Is Brake Fluid?
Brake fluid is a hydraulic fluid that transfers the pressure from your foot on the brake pedal to the brake calipers, causing your vehicle to slow down or stop. It must withstand extreme temperatures and high pressure while maintaining consistent performance.
เมื่อเวลาผ่านไป, brake fluid can absorb moisture (especially DOT 3 and DOT 4), reducing its effectiveness and safety. That’s why choosing the right type—and changing it at proper intervals—is crucial.
Key Differences Between DOT 3, DOT 4, and DOT 5 Brake Fluids
Here’s a quick comparison table to get us started:
| คุณสมบัติ | DOT 3 | DOT 4 | DOT 5 (Silicone) |
|---|---|---|---|
| Base Component | Glycol Ether | Glycol Ether | Silicone |
| Dry Boiling Point (°F) | ~401°F | ~446°F | ~500°F |
| Wet Boiling Point (°F) | ~284°F | ~311°F | ~356°F |
| Absorbs Water? | ใช่ | ใช่ | เลขที่ |
| Paint Damage Risk | สูง | สูง | Low |
| Compatibility | With each other | With each other | NOT with DOT 3/4 |
| ABS Compatibility | ใช่ | ใช่ | เลขที่ (foams easily) |
| Typical Use | Older cars | Most modern cars | Classic & specialty vehicles |
DOT 3 ของเหลวเบรก: Reliable and Affordable
If you drive an older vehicle or don’t push your brakes too hard (เช่น, no aggressive braking or mountain driving), DOT 3 brake fluid might be enough.
ผู้เชี่ยวชาญ:
-
Cost-effective and widely available.
-
Ideal for light-duty, non-performance vehicles.
Cons:
-
Lower boiling point (can cause brake fade under heavy use).
-
Absorbs moisture easily, requiring more frequent changes.
DOT 4 ของเหลวเบรก: A Step Up for Modern Vehicles
DOT 4 is similar in base to DOT 3 (both are glycol-based), but it offers higher boiling points and better performance.
ผู้เชี่ยวชาญ:
-
More heat resistant—better for high-speed or aggressive braking.
-
Often recommended for vehicles with ABS.
Cons:
-
Slightly more expensive than DOT 3.
-
Still absorbs moisture and can damage paint.
DOT 5 ของเหลวเบรก: Specialty Choice (But Not for Everyone)
DOT 5 brake fluid is silicone-based, and this makes it fundamentally different. It doesn’t mix with water, making it more stable over time—but also less forgiving in systems not designed for it.
ผู้เชี่ยวชาญ:
-
Doesn’t absorb moisture.
-
Won’t damage paint on contact.
-
Long shelf life.
Cons:
-
Incompatible with DOT 3 and DOT 4 systems.
-
Can aerate (foam) easily—bad for ABS systems.
-
แพงกว่า.
Can You Mix DOT 3, DOT 4, and DOT 5 Brake Fluids?
This is where it gets critical.
| Mixing Scenario | Safe or Not? | Explanation |
|---|---|---|
| DOT 3 + DOT 4 | ✅ Yes | Compatible due to similar chemical base (glycol-based). |
| DOT 3/4 + DOT 5 | ❌ No | DOT 5 is silicone-based and won’t mix—can cause system failure. |
| DOT 5.1 + DOT 4/3 | ✅ Yes | DOT 5.1 is glycol-based (despite name), safe to mix. |
Important Note: DOT 5 (silicone-based) and DOT 5.1 (glycol-based) are not the same. Always double-check the label.
Which Brake Fluid Should You Use?
Here’s how I decide:
-
Daily driving in a regular car? Use DOT 4.
-
Older car with minimal performance needs? DOT 3 is enough.
-
Classic or show cars (non-ABS)? DOT 5 might work.
-
High-performance or track use? Consider DOT 4 or DOT 5.1 for higher boiling points.
Always consult your vehicle owner’s manual before adding or replacing brake fluid.
คำถามที่พบบ่อย
Q: Can I switch from DOT 3 to DOT 4?
ก: ใช่, DOT 4 is compatible and can be used to replace DOT 3. It’s actually an upgrade in performance.
Q: How often should I change my brake fluid?
ก: Generally every 2 ปี, but it depends on the fluid type and vehicle. Check your manual.
Q: What happens if I use the wrong brake fluid?
ก: Using incompatible fluid (like mixing DOT 3 with DOT 5) can cause brake failure or system damage.
Q: Is DOT 5 better than DOT 4?
ก: Not necessarily. DOT 5 is better in terms of moisture resistance, but it’s incompatible with most modern braking systems.
Q: What is DOT 5.1 then?
ก: DOT 5.1 is a glycol-based fluid (like DOT 3/4) with high performance. It’s compatible with DOT 3 และ 4 systems.
Final Thoughts
Choosing the right brake fluid may seem minor, but it has a huge impact on your safety. Knowing the difference between DOT 3, DOT 4, and DOT 5 brake fluids helps you make better maintenance decisions, avoid costly damage, and keep your brakes functioning optimally.
If you’re unsure, play it safe—stick with what your car manufacturer recommends, and always avoid mixing incompatible types.
