What kind of brake fluid does a 1967 Austin Healey 3000 use.It says "Use only Gerling Brake Fluid".Is that mineral spirits?
The 1967 Austin-Healey 3000 MK3 2.9L 1BL 2 Carb OHV 6cyl uses either DOT 3 OR 4 Brake Fluid.
http://classicgarage.com/luprmioil.html
Note: Conventional brake fluid should not be mixed with mineral oil fluid. Serious damage may result. Consult manufacturer's handbook for details.
If you have been using Lucas Premium Mineral Oil, I would continue to use it.