[Healeys] brake fluid(again)

[healeymanjim at hansencc.net]

just rebuilt a servo in a club members bj8.  i now realize that the only brake flluid i have is synthetic, which is all that is available. this car has never had any of the brake or clutch parts rebuilt to her knowledge and she has owned it since picking it up at the factory in 1965.  is this new brake fluid going to eat up all the old rubber, which i assume is natural rubber and not compatable with anything but the old castrol or lockheed type fluid?  i guess i can warn her to beware, but sure would hate for her to lose her brakes again.  anyone up on all this?   hjim