Castrol React SRF Racing Brake Fluid

React SRF is the endurance-racing benchmark and, by wet boiling point, arguably the most capable brake fluid you can buy. Its unusual silicone-ester chemistry absorbs far less water than conventional glycol fluids, so it holds an exceptional 270°C wet boiling point — where ordinary DOT 4 racing fluids have long since degraded, SRF is still delivering a firm, fade-free pedal deep into a race stint.

That moisture resistance also gives it a longer, more stable service life between flushes. It's a premium, pro-level fluid: overkill for a casual street car, exactly right for serious HPDE, time attack, and wheel-to-wheel racing. DOT 4 compatible and mixes with conventional DOT 3/4 fluid for bleeding.