From a Castrol Oils, Inc technical bulletin (undated, but still useful information):
“Motor oil has been termed the ‘life-blood’ of the engine. If the engine fails to start. the vehicle simply won’t go. If the oil fails to lubricate properly, the engine will wear out prematurely. But the BRAKE FLUID is the LIFE-BLOOD of the Entire Vehicle. If the brake system fails, the vehicle will not stop! Eventually it will stop, of course, but more than likely it will stop quite suddenly. And the entire vehicle may ‘wear out’ immediately!
… Brake fluids, in a very short period of time, do attract and absorb moisture, especially under conditions of high humidity. This moisture combines with the fluid, lowers its boiling point, and increases the chanced of vapor lock formation. Castrol GT LMA, with its unique Low Moisture Activity. is less affected by absorbed moisture, and has a greater ability to expel it under conditions of reduced humidity and to regain a higher boiling point and a higher ‘vapor lock temperature.’
… But even the best fluid unavoidable will become contaminated in service with moisture, wear materials, dirt, grit, or oil, and the only to rid the system of such contaminants is to drain the fluid completely and replace it with fresh new fluid. Girling engineers recommend emphatically that brake fluid be changed every 18 months, and the entire system overhauled after 40,000 miles. … Always maintain the proper fluid level. Drain the system and renew the fluid at regular intervals, sooner in severe operation or under high heat or humidity conditions, or if contamination is supected. If your engine fails, you won’t go. If your brakes fail, you’ll wish you’d gone — to Castrol GT LMA.”
Castrol GT LMA was originally “Girling Amber”, the highest performance of three brake fluids made by Castrol for Girling, one of the largest brake manufacturer in Europe. When the US Dept of Transportation put out the DOT 4 specification, the LMA met it with flying colors, and became the basic fluid for most Girling systems. The exception was Rolls Royce, whose vehicles have a hydraulic suspension tied into the brakes which was designed for Girling Crimson. Rolls reformulated this for their own use and now sell it as RR363. (Later Rolls vehicles use Hydraulic Systems Mineral Oil which is totally different and not interchangeable.)
We only use DOT 4 fluids in our shop and insist that our customers use only DOT 4 brake fluid in all European and Japanese cars. Some of the reservoir lids say DOT 3, but that may have been the best available at the time. We have found that many of the DOT 3 fluids are not compatible with the natural rubber compounds used in many braking systems. The natural rubber seals are solfter and perform better than synthetics, but they are more sensitive to chemical attack. We have taken apart too many braking systems that have little lumps of tar that used to be brake seals and a can of cheapie brake fluid in the car. One Saturday a gentleman came in the store with the guts out of his Audi master cylinder in his hand. It looked like microscopic mice had nibbled the edges of the seals. His father-in-law had topped off his master cylinder with whatever he happend to have in his garage. Not helpful! If you notice your brake fluid turning black or developing little black specks floating in it, be aware that is rubber being eaten by your brake fluid.
- Castrol GT (LMA) 12 oz and 32oz
- British Lockheed DOT4
- Pentosin DOT4
- Ate Blue DOT4
- Ate Super Blue
- Castrol RR363 for Rolls/Bentley -78
- GMF2100 or JLM9886 for Rolls/Bentley 79-