RR363 Rolls-Royce Brake Fluid: What’s all the Fuss?

In the Rolls-Royce fraternity, nothing seems to cause more controversy than Rolls-Royce Brake Fluid: Castrol RR363 hydraulic fluid. Any mention on a forum or chat room seems to generate acres of comment, with any number of views (some very vociferous). After all, RR363 is just a glycol-based oil, very similar to DOT3 and DOT4 synthetic oils. So why all the fuss?

Deep breath.

When the Silver Shadow series was introduced, Rolls-Royce originally recommended DOT3 brake fluid, and it’s true – you can use it without causing irrevocable damage to the complex hydraulic system of your Rolls-Royce Silver Shadow, Bentley T-Type or Corniche (take note, though, from chassis 50001 (1980) Corniche onward you must use green mineral fluid). Pretty soon after the Silver Shadow (etc.) was introduced, owners started to complain about funny knocks and squeaks, particularly from the hydraulic rear height control rams. To cure this, Rolls-Royce Motorcars Limited developed the Rolls-Royce Brake Fluid RR363 with Castrol Oils. RR363 cured the squeaks, and everyone lived happily ever after.

Except they didn’t.

Most people know that Castrol added a certain amount of castor oil to the glycol base. Well, DOT3 is cheap, and castor oil is cheap, why not mix a bit up at home? Job done.

Not quite. The problem is that the viscosity of DOT3/4 and caster oil is different. If you leave it in a jar (or in the reservoir of your Rolls-Royce or Bentley braking system) it will separate, and one oil will float on top of the other. If they’re separate, you won’t get the benefit of both parts. Castrol solved this by adding a chemical dispersant to the oil, which keeps the caster oil evenly dispersed through the base oil.

That’s why we recommend RR363 Brake Fluid, and our customers drive squeak-free Rolls-Royce motorcars…

Check the RR - Technical Video Library for more.