5-LED Brake Fluid Tester Pen – DOT3/DOT4/DOT5 Oil Quality Check

Know Your Brake Fluid's Condition in Seconds

Don't wait for brake failure to tell you something's wrong. The Shunmaii 5-LED Brake Fluid Tester gives you an instant, accurate read on the water content in your brake fluid — right from your driveway. Compatible with DOT3, DOT4, and DOT5 brake fluids, this compact diagnostic pen is an essential safety tool for every driver, mechanic, and car enthusiast.

Made in Mainland China.

Why Water in Brake Fluid Is Dangerous

Brake fluid is hygroscopic — it naturally absorbs moisture over time. Even a small amount of water lowers the fluid's boiling point, which can cause brake fade, spongy pedal feel, or complete brake failure under heavy use. Regular testing with this pen helps you stay ahead of costly repairs and keeps you and your passengers safe. Learn more about vehicle brake safety from the National Highway Traffic Safety Administration or visit the U.S. Consumer Product Safety Commission for general automotive tool safety guidance.

How the 5-LED Indicator Works

• 🟢 Green only: Brake fluid is in excellent condition — no water detected.
• 🟢🟡 Green + 1 Yellow: Water content <1% — fluid is performing well, no action needed.
• 🟢🟡🟡 Green + 2 Yellow: Water content ~2% — fluid is still usable; re-test in 6 months.
• 🟢🟡🟡🔴 Green + 2 Yellow + 1 Red: Water content ~3% — brake fluid replacement recommended soon.
• 🟢🟡🟡🔴🔴 All 5 LEDs: Water content ≥4% — replace brake fluid immediately for your safety.

Key Features

• Instant Results: Get a clear water-content reading in seconds — no waiting, no guesswork.
• Highly Accurate: Precise electronic sensor delivers reliable diagnostics every time.
• Universal Compatibility: Works with DOT3, DOT4, and DOT5.1 brake fluids across most vehicle makes and models.
• Durable ABS Construction: Built to handle repeated use in garage and workshop environments.
• Beginner-Friendly: Single-button operation — press, dip the probe, read the LEDs. That's it.
• Auto Power-Off: Shuts off automatically after 12 seconds of inactivity to save battery life.
• Compact & Portable: Pen-style form factor fits easily in a glove box, tool bag, or kit.

Specifications

How to Use

1. Power On: Press the button — the green LED should illuminate. If it doesn't, replace the battery.
2. Open Reservoir: Unscrew the cap on your vehicle's brake fluid reservoir.
3. Dip the Probe: Remove the tester cap and submerge the probe tip into the brake fluid.
4. Read the LEDs: The lit LEDs instantly show the water percentage in your fluid.
5. Replace Cap: Securely tighten the brake fluid reservoir cap after testing.
6. Auto-Off: The tester powers down automatically after 12 seconds.

What's in the Box

• 1 × Brake Fluid Tester Pen

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Learn more: Brake fluid

Frequently Asked Questions

Q: What types of brake fluid is this tester compatible with?

A: The Shunmaii brake fluid tester is compatible with DOT3, DOT4, and DOT5/DOT5.1 brake fluids, making it suitable for the vast majority of passenger cars, trucks, motorcycles, and SUVs on the market today.

Q: How often should I test my car's brake fluid?

A: Automotive experts generally recommend testing brake fluid quality at least once a year or every 20,000–25,000 miles. If the tester shows a Yellow warning (1.5%–3% water content), re-test after six months. If Red LEDs light up (water content ≥3%), replace the brake fluid immediately for safe braking performance.

Q: Do I need any technical skill to use this brake fluid tester?

A: Not at all! The single-button operation and intuitive 5-LED color display make it simple for beginners and professionals alike. Just press the button, dip the probe into the brake fluid, and read the colored LEDs — the whole process takes under 30 seconds.

Q: What does it mean when all 5 LEDs light up?

A: When all five LEDs (green, two yellows, and two reds) are illuminated, your brake fluid has a water content of 4% or higher. This is a critical threshold — you should replace your brake fluid immediately, as excessively contaminated fluid significantly reduces braking effectiveness and can be dangerous.