Brake Fluid for DB9

[cuddapah]

For my 2015 DB9, manual says Brake Fluid to use is 'React Performance DOT 4'. I understand AM uses Castrol React Performance DOT 4 which I couldn't find here in USA anymore. Is there a good substitute that can be used ?

[Manx V8V]

As far as I am aware the brand isnt a major issue, the spec (DOT 4) which is the boiling point and other factors are the same.

[8Tech]

Any quality DOT4 or better will be fine. I use DOT5.1 as it is a higher spec. Note, you cannot use DOT5 as this is a silicon based synthetic fluid and will not mix with the DOT4 in the system.

[telum01]

I use Motul RBF600 in my red V8V and Motul RBF660 in my grey V8V. For most people, Motul DOT5.1 (or comparable) is perfectly fine.

Here's a comparison of Motul and Castrol brake fluids:
http://www.redpants.lol/brake-fluid-comparison/

The easiest way to explain wet vs dry boiling points is that new fluid is dry, and old fluid is wet. "Wet" refers to the fluid's absorption of water over time. "Dry" means it hasn't absorbed any water yet. Water doesn't withstand boiling very well, so old (wet) fluid boils more easily than new (dry) fluid. When brake fluid boils, you get steam where fluid should be, and steam compresses. That's important to know (and avoid!) because that compressing steam takes away from your brake pressure. The end result is your brake pedal goes to the floor and you still can't stop.

Bit of a tangent, but the point is that you need a brake fluid for your use. For normal street driving, Castrol React or Motul DOT5.1 work great. But if you drive aggressively, you'll want something that can handle the extra temperatures.