[shadow 11]

It's time to flush and change my brake Silver Shadow 11 brake fluid again. In the past I have used Castrol DOT3 RR363 or DOT3 with castor oil and more recently DOT4 with castor oil and now I'm considering DOT5.1 and castor oil. All the above are glycol based with progressive improvements in formulation over the years. Does anyone know of a reason not to use DOT5.1?.Just thought I'd check before biting the bullet.

 

[guyslp]

I wouldn't use DOT5.1 not because I think it would be a problem, but because of expense.

We have to change the brake fluid in these cars so much more frequently than is typical there is no consideration of "extending life" at all. DOT3 (or DOT 4) are just fine if you're making YAK363 (the addition of 10% castor oil) with them.

 

[shadow 11]

That's a good point Brian, I hadn't checked the cost of DOT 5.1, I can buy 5 litres of DOT 4 for €30.

 

[hanscars8l]

DOT 5 brake fluid is NOT glycol based!
That is silicone fluid which cannot be used in Silver Shadow hydraulic systems with or without castor oil.!9

 

[shadow 11]

DOT 5 is silicone, I'm talking about DOT 5.1 which is glycol based.

 

[guyslp]

I'm talking about DOT 5.1 which is glycol based.

Yep. And why in heaven they decided to just use a dot designation for a formulation with an entirely different base (and an old one) eludes me to this day. I don't think there have been many more decisions in the world of specifications that have wrought as much confusion as DOT 5 (silicone) and DOT 5.1 (glycol) designations for radically different fluid compositions.

 

[epstanwyck]

I've used straight Castor oil for years without any problems. It' sure as heck cheaper!

 

[Wraithman]

How cold does it get where the car is used?

 

[KiloKilo]

Seems that there is still some discussion on the best oil/mix.
Could I ask which one (or mix) is most used? As it is clear there will be a need for often changing it would be key to get it right I guess. And anon-mix would of course make life easier...

Is there one that has the majority of the community use?

 

[Dounraey]

I've been on this forum for about 10 years and from the entries I have read most use a 90-10% mix. I've been using this mix for 9 years with no issues at all. I use DOT3 and aircraft model engine grade castor oil, although most people use pharmaceutical grade castor oil. Would be interesting to hear other owners views on this.

 

[Wraithman]

I have cars with 90/10 (DOT4/Pharma) in service for over 5 yrs with no issues and too lazy to do a needed flush thru. Believe it or not many of the cars with high mileage and wear on the brake pumps seem to survive on straight DOT3/4. The original fluid in early 1966 was straight brake fluid and the factory soon discovered pump issues, hence the RR363.with lubricant.developed by Castrol aka Cas-ter Oil.

 

[Dounraey]

It's worth mentioning that Brian Vogel has kept the 90/10 mix as a test sample for years where it has been subjected to winter low and summer high temperatures with no separation of the mix.

 

[KiloKilo]

Hi Dounraey,
That is useful to know. Just saw a YT clip where RR363 was discussed vs mixes and they did warn against a mix due to separation.

 

[guyslp]

I've still got that sample in my garage (unheated, not temperature controlled in any way) and added way more water to it than would ever be absorbed from the atmosphere as part of my experiment. Still never a bit of separation.

I've used a 90% DOT3, 10% castor oil mix in both my cars. I need to look in SRH33576, as she's overdue (very) for a change, but I suspect this mix will be far less ugly than what I've seen with RR363. I still cannot for the life of me figure out what the "algae like substance" is that seems to form in RR363 that's left too long between changes.

 

[Dounraey]

I checked out the Youtube video that KiloKilo mentioned and watched the part where the presenter said not to use the mix due to separation. I was surprised as the statement runs counter to the experience of all the owners who have commented on this forum over the past 10 years, not to mention my own experience and Brian's research. Then I noticed the video was made by Introcar who just happen to market RR363 .........