Castrol SRF - fit and forget . It's wet boiling point (270°C !) is higher than that of most 5.1s DRY boiling point . Downside is, it's expensive - BUT it does not need changing as often, so works out no more expensive in the long term . My SRF has now been in the car for 5 years and I have had no problems, although I think I really should change it now .

See issue 254 of Fast Ford for full details . Just do a Google search for brake fluids, compare the wet and dry boiling points and you will see for yourself that NONE come close to matching Castrol SRF .