Originally Posted by v4voodoo
If 446F/311F dry/wet boiling point* is not rubbish, what is? Between an E36 M3, an E46 M3, an 05 Z4 and an 07 335i I have never driven a BMW with OEM fluid whose brake pedal didn't get mushy after a couple of hard high speed stops.
*Belarus stats, not verified by me. I actually think it may be even worse than that.
Sine you've been having mushy brake pedal with all of your cars (I'm assuming during your daily drive) after only slamming few times on the brakes (surprised you din't put that brake pedal through the floor... cough..cough) just use Castrol SRF - DOT 4 - 590ºF (310ºC) / 518ºF (270ºC),
if that doesn't help, then you're SOL until a special brand comes out for your heavy brake pedal foot. While you're at it also upgrade to StopTech or Brembo GT at least 6 pitson front and 4 piston rear BBK.
BTW I'm interested how often you change your brake pads and rotors... hmmm every 10K miles...