I’ve got Castrol React Performance in at present
It has boiled on me in the past but has been OK since regular bleeding
Thought I might go with the higher boiling point Motul 600.
Can I just start adding Motul in at the top end or does the whole system need draining?
Think you know the answer to that one !
If you’ve breached the limits of the castrol and are replacing with new fluid then you’ve gotta make sure to expel the old fluid or the whole exercise is pointless ?
I’ve gone over to ATE superblue , coloured thus so it’s easy to see when the old fluid is expelled .
Having said that ,it’s generally accepted that SRF is the fluid to die for …
Needs regular changing tho as it’s very hydroscopic ,wouldn’t suit me I’m sure …
Motul RBF 600, Motul RBF 660 or Performance Friction RBF665 are all at least as good, probably better and less hydroscopic than SRF…and cheaper.
If you do change fluid then change it all would be my advice.
I’ve used SRF to great effect for years and it doesn’t need changing that regularly. Once a year is fine.
RBF 600 for me, never had a problem since and way cheaper than SRF
Drain the master cylinder with a syringe refill with new then bleed all the lines, easy 
Best change my SRF then, It’s been in there for 2 years now. Think I’ll go with Stephens advice, Saying that I do bleed on a regular basis and I have had no problems, car is only used as a track toy too
SRF for years in mine - change it every year.
Thanks Guys,
The question was worded in a fairly numpty way as I was more concerned about the 2 products sludging abit like blue and orange coolants, however, your advice was appreciated. Motul 600 in the system and generally flushed to the probable complete exclusion of the castrol.
Just need a handbrake now. Come on DHL , chop chop.
Waiting on 2 things from DHL all rather annoying, be good to get my car back a bit before Anglesey rather than on the way there!