All conventional brake fluids used in cars and motor cycles are hygroscopic, that is, they absorb water from their surroundings. Strange though it may seem, the flexible hoses incorporated in braking systems are permeable to water and in time enough, water can find its way into the system via the hoses, and seriously affect the brake fluid's performance. This water reduces the boiling point of the fluid (ie, it lowers the temperature at which gas bubbles begin to form). When these bubbles form, they turn a virtually incompressible liquid into a mixture of gas and liquid which can be compressed quite considerably, thus severely reducing the efficiency of the brakes. In this situation, a driver finds that the brakes feel spongy. Brake-pedal travel will increase and it may be necessary to 'pump' the pedal to get the brakes to function effectively. However, when the brake fluid reaches a temperature at which the water in the fluid causes gas to be produced, which is equal to the volume swept by the piston in the rake master-cylinder, vapor-lock occurs and the brakes become inoperative. When this happens, the first indication the driver has that something is wrong is when he applies the brakes. The pedal goes down to the floor and the car carries on at undiminished - and possibly fatal speed.

The silicon ester technology in Castrol SRF addresses this problem in two ways. Firstly, Castrol SRF is less hygroscopic than conventional brake fluids - it absorbs less water in a given time. Secondly, unlike conventional glycol ether fluids, Castrol SRF reacts chemically with the absorbed water to reduce its adverse effects, thus preventing the fluid's high temperature performance and safety margins from deteriorating as rapidly as they would otherwise do.

Castrol SRF Brake Fluid is a DOT 4 brake fluid suitable for all disc and drum brake systems except those prescribed for mineral oil. Castrol SRF is a high-performance product. Castrol SRF Brake Fluid's unique silicon ester technology absorbs less water than conventional glycol ether fluids and prevents the fluid's high temperature performance from deteriorating. Its wet boiling point of 270°C (518°F) is vastly superior to the minimum requirement of 155°C demanded by the current US DOT 4 specification. Its ability to withstand temperatures in excess of 300°C and superior resistance to the effects of absorbed water have established Castrol SRF Brake Fluid as the world's premier fluid for the hydraulic brakes used in all forms of motorsport and racing. 1 Liter Bottle.