Well, I am getting jumped on before any of you have read the spec.s of both the Vavoline and Castrol system synthetic DOT 3 or 4 fluids.
Hers is what I just pulled of line for Castrol,
"Perfect size for topping off your brake fluid level! (12 oz.)
Provides Superior Synthetic Lubrication for Anti-Lock Braking Systems (ABS).
Recommended for all U.S. and foreign vehicles with DOT 3 and DOT 4 requirements, including Land Rover and BMW.
Exceeds DOT 3 and DOT 4 requirements.
Unique Low Moisture Activity (LMA) formulation provides maximum protection against vapor lock brake failure.
Synthetic formulation maintains a higher boiling point than conventional brake fluids.
Superior protection against chloride and zinc corrosion of braking system parts.
Ideally suited for Land Rover and BMW / MINI Cooper vehicles as well as Audi, Jaguar, Mercedes-Benz, Porsche, Saab, Volkswagen, Volvo, Honda, Acura, and many other brake systems.
Exceeds specifications SAE 1703, SAE 1704, ISO 4925, JIS K2233 and FMVSS No. 116 DOT 3 and DOT 4. "
Same thing as what Vavoline states.
So, let's don't be so quick to try and make someone be wrong.