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How we reviewed this product: we studied the manufacturer's specifications, materials, included parts and warranty terms, read owner feedback where available, and compared it with similar products. We did not run our own lab tests.

Motul's RBF 600 is a track day favorite. RBF 660 raises the dry boiling point further for long stints, heavy cars and very high brake temperatures.

Quick verdict

  • Best for: serious track use, endurance racing and carbon or big brake systems.
  • Type: 100% synthetic polyglycol DOT 4 racing fluid.
  • Strengths: very high dry and wet boiling points, nitrogen-filled bottle.
  • Watch out for: normal viscosity, so it is not ideal for street cars that need low-viscosity fluid.

Key numbers (Motul data)

  • Dry boiling point: 325 °C (617 °F).
  • Wet boiling point: about 205 °C (401 °F).
  • Standards: FMVSS 116 DOT 4, SAE J1703 and J1704.
  • Viscosity at −40 °C: about 1,698 mm²/s, which is why it does not meet DOT 5.1 cold-flow limits.

RBF 660 vs RBF 600

Retailers list RBF 660 at 325 °C dry versus about 312 °C for RBF 600, with the same wet boiling point. The extra margin matters mainly for long sessions and very hot brakes.

How to use it

  • Flush the whole system; do not mix with lower-grade fluids.
  • Change it often if you track the car.
  • BMW specialist BimmerWorld notes that cars used on the street as well should stay on the factory-type fluid.

Pros and cons

Pros

  • Huge heat margin
  • Long shelf life while sealed

Cons

  • Overkill for daily driving
  • Small 500 ml bottles

Before you buy brake fluid

  1. Check your owner's manual or the reservoir cap for the fluid your vehicle needs.
  2. Never use DOT 5 (silicone) fluid unless your system is designed for it, and never mix it with glycol fluids.
  3. Only open a new, sealed bottle. Brake fluid absorbs moisture once opened.
  4. Brake fluid damages paint. Wipe up spills right away.

Safety note: brakes are safety parts. If you are not sure how to do the job, have a qualified mechanic do it.

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