The Motul RBF 660 Factory Line is a 500 ml (1/2 L) bottle of 100% synthetic, polyglycol-based DOT 4 racing brake fluid, MPN 101667. The manufacturer's data sheet lists a dry boiling point of 328°C (622°F) and a wet boiling point of 204°C (399°F). The formula targets the heat from carbon and ceramic discs, where the manufacturer says it limits air entry during brake cooling. The manufacturer states it widely exceeds DOT 3, DOT 4 and DOT 5.1 standards.
Stock DOT 3 or 4 fluid leaves far less thermal margin for repeated heavy stops, and a higher dry boiling point is what keeps the pedal firm when fade would otherwise set in. One owner on a user forum noticed a pedal feel improvement after switching to this fluid. Keep in mind that another forum user favored RBF 600 for its higher wet boiling point of 421 versus 399 for the RBF 660, so choose based on how often you refresh fluid. Fitment is broad: the fluid suits hydraulic brake and clutch systems, and the manufacturer says it can also be used with conventional steel discs and clutch actuators. Searchable terms this fits include RBF 660 DOT 4 track fluid, non-silicone racing brake fluid, and carbon ceramic brake fluid for track days.
The manufacturer describes RBF 660 as a DOT 4 fluid for hydraulic brake and clutch systems that require a non-silicone synthetic fluid. Confirm your owner's manual specifies DOT 4 before switching, and avoid putting it into any system that currently uses silicone DOT 5 fluid.
Owners on user forums say RBF 600 has the higher wet boiling point, while RBF 660 is generally chosen for extreme carbon or ceramic braking. Forum users suggest RBF 600 if you will not replace the fluid before each event.
Owners on user forums warn that leftover OEM fluid dilutes the new fluid and can reduce its performance, so a complete flush is the safer approach.
This is a fluid change rather than a part install, so it suits a home mechanic who is comfortable bleeding brakes. Gather a wrench for the bleeders (owners on user forums note most are 8mm), a clear hose, a catch bottle, and a helper for the pedal or a pressure bleeder. Owners on user forums recommend emptying the master cylinder and refilling with fresh fluid before pressurizing the system, then bleeding in a set order; one Corvette owner started at the right rear caliper and finished at the right front. Brake fluid absorbs moisture from the air, which lowers its boiling point, so keep the bottle sealed and do not leave the system open longer than necessary.
