Castrol SRF

Author
Discussion

Jasmine1

Original Poster:

163 posts

90 months

Tuesday 1st August 2023
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How often are you guys changing out your Castrol SRF?

I last did a brake fluid change in January; I've done two track days since then (and a set of pads) but the pedal feel is still excellent.

Should I consider changing it soon, or can I leave it for another 18 months as per the usual interim for brake fluid? I'll likely do one or two more track days in that time.




jj.

557 posts

277 months

Tuesday 1st August 2023
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Did mine in November last year. Have done 5 days since, ran 2 x sets of pads down to 2mm/3mm, and a Donington evening session yesterday on a new set of pads.

When first installed, I was bleeding each corner as pedal was going a little longer after each day. Haven’t done so now for the past 2 days, and feels nice and firm. I won’t change mine for another year yet, as feel last night was the best I’ve had. It is fantastic fluid. Although I do also run cooling ducts for the fronts (63mm hose’s) which helps.

When I used to race on it, we never changed it over a 3 year period, just bleed 2 pedal pumps after quali and before race. It was always perfect.
jj

matt5964

85 posts

23 months

Tuesday 1st August 2023
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Change ours yearly, as it’s Dot4 and more hygroscopic, but having said that the wet boiling point is so high it’s almost other makes dry point, so maybe overkill yearly

For reference it goes in a Lotus Elise RGB , running Alcon rotors alloy bells and CL5+ pads
We do about 8-10 track days a year and plenty of road miles

Paul_M3

2,417 posts

192 months

Tuesday 1st August 2023
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Castrol themselves recommend changing it every 18 months.

Edit: There seems to be some internet myth about SRF needing to be changed more frequently than other high performance brake fluids. I'm not sure where that's come from, and I've seen some people say it needs changing every 6 months.

A) I doubt anyone on the internet knows the exact formula of SRF and how hygroscopic it is.

B) It's a DOT 3 & 4 fluid. Most of the other well known alternatives such as Motul RBF 600/660 and Gulf RF1000 are also DOT 4 fluids.

C) If you're going to change your fluid very frequently, you're not really getting the benefit of the SRF's wet boiling point, and you may as well use a cheaper fluid which has an equal or better DRY boiling point. (Motul 660 actually has a higher dry boiling point than SRF)

Edited by Paul_M3 on Tuesday 1st August 21:44

Jasmine1

Original Poster:

163 posts

90 months

Sunday 6th August 2023
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Thanks for the feedback.

You're right, even Castrol says the life of SRF is 18 months.

Maybe I've read a few too many scare stories from yesteryears where people claimed you needed to flush it out every few months or every two track days.

brillomaster

1,396 posts

177 months

Monday 7th August 2023
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if you have some mechanical sympathy and concept of heat management, then every 18 months is fine. might be an idea to check if you have some kind of front brake air cooling, some supposedly sporty cars have none and if you can put some in, it does help keep brakes cool.

similar argument with engine oil - some change it after every trackday, but this seems overkill to me, as long as you dont overheat your engine in the first place - either sort your cooling system out, or shorten your stints so you arent overheating.

braddo

11,253 posts

195 months

Monday 7th August 2023
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Jasmine1 said:
I last did a brake fluid change in January; I've done two track days since then (and a set of pads) but the pedal feel is still excellent.
jj. said:
Did mine in November last year. Have done 5 days since, ran 2 x sets of pads down to 2mm/3mm, and a Donington evening session yesterday on a new set of pads.

jj
A set of brake pads is lasting only 2-3 track days?!

brillomaster

1,396 posts

177 months

Monday 7th August 2023
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depending on the pad, sometimes even less than that! i've been through a set of standard brembo front pads on my boxster in little over 5 hrs - they were terrible.

ebc blues lasted me 2-3 days, and then a decent set of pads (PF08, Pagid RS42) last half a dozen days or more.

jj.

557 posts

277 months

Monday 7th August 2023
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braddo said:
A set of brake pads is lasting only 2-3 track days?!
Yup.! I did a set of EBC Yellows in 1/2 day at Bedford (dry) then 1 full day at Snett (wet) - the wet running literally was slicing the material off. 2mm left when I checked at home.
EBC Blues 1 Full Day at Don, and 2 x 1/2 day Don, was about 3mm left, but not enough for another day.
Spoke to EBC they suggested to add cooling.
Now gone up to a RP1 Pad (Full Race - Orange on the rear) and the feel is excellent, as is the pad life - I think the cooling has really helped.
When racing 45mins endurance used to only get 1 race and maybe 2 x quali from a set of Carbotech pads, then they were toast.!
I wouldn't trust a set of pads at 2mm, so would swap then out.
jj