[SEL] OT. Brake fluids

[curt at rustyiron.com]

Years ago one had to be careful when servicing foreign cars about
computability with brake fluids. I'm not speaking of the silicone brake
fluid, but rather the regular (glycol?) brake fluids. Seems like most
European cars used Castrol brake fluid and I was taught to only use
Castrol brake fluid in these cars, lest the rubber parts soften and lead
to brake failure.
Is this still the case?

I found nothing about this on a quick Internet search, so maybe the issue
has been resolved.

My sister has a newer VW and they added brake fluid (not Castrol) they
bought at a local auto parts store. Just wanted to make sure she doesn't
have an issue later.
Curt Holland