Home Safety / Products / Brake fluid (DOT 3/4)

Brake fluid (DOT 3/4) — household safety profile

Elevated risk

Hydraulic brake fluid based on polyethylene glycol ethers (polyalkylene glycol).

What is this product?

Hydraulic brake fluid based on polyethylene glycol ethers (polyalkylene glycol). DOT 3 and DOT 4 are the most common consumer grades. Contains glycol ethers that are skin/eye irritants and CNS depressants at high exposure. Ingestion causes metabolic acidosis similar to ethylene glycol poisoning. Attacks paint and most plastics on contact. Hygroscopic — absorbs atmospheric moisture over time, lowering boiling point and degrading brake performance.

What's in it

Click any compound name for its full safety profile, regulatory consensus, and exposure data.

Base Fluid

  • Polyethylene glycol 400 (PEG-400) — Glycol ethers absorbed through skin. CNS depressant. Metabolized to organic acids causing metabolic acidosis if ingested. Less toxic than ethylene glycol but still hazardous.

How to use it more safely

  • Wear nitrile gloves and safety glasses during brake service
  • Work in ventilated area
  • Clean spills immediately — attacks paint and rubber
  • Cap reservoir promptly (hygroscopic)

Safer alternatives

  • DOT 5 silicone brake fluid — Non-hygroscopic, non-corrosive to paint; not compatible with DOT 3/4 systems without full flush

Frequently asked questions

What's in Brake fluid (DOT 3/4)?

This product type can contain: Polyethylene glycol ethers, among others. Click any compound name above for the full safety profile.

How can I use Brake fluid (DOT 3/4) more safely?

Wear nitrile gloves and safety glasses during brake service; Work in ventilated area; Clean spills immediately — attacks paint and rubber

Are there safer alternatives to Brake fluid (DOT 3/4)?

Yes — consider: DOT 5 silicone brake fluid. See the Safer alternatives section above for details.

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Reference data, not professional advice. Aggregates publicly available regulatory and scientific information. Why we built ALETHEIA →