Brake Fluid

[march2020]

I purchased a NOS factory master cylinder for the '77-'80 MGB, made by Girling or Lucas i can't remember. It's not an aftermarket one. It is a new one the factory would have used back in the day.  It's also not recently made.I would guess it was made in the late 70's.  I bought it because I want original quality.  The question for you is which brake fluid should I use?   
I ask because I read of 'natural rubber' in older systems or even SBR type rubber from the 70's being not compatible with borate esters in DOT4.  I don't want to ruin a nice NOS master cylinder.  What do you think? 
Rick Lazio

[JohnTwist]

hose warnings about brake fluid were valid before about 1970.  My suggestion is to use DOT 4.  DOT 3 is OK, too, but DOT 4 removes paint a little slower.  Hope this helps.
John H. Twist
SAFETY FAST!
616-307-6737
johntwist@universitymotorsltd.com
www.universitymotorsltd.com