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Advice against silicone-based brake fluid (Castrol SRF)? - Ride/Handling/Suspension/Brakes/Wheels/Tyres - The Lotus Forums Jump to content

Advice against silicone-based brake fluid (Castrol SRF)?

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When approaching the service for an Exige, I've been a little bit unexpectedly told that the dealer would not use Castrol SRF (which I strongly prefer) as it is silicone-based. I've asked for explanation for such position and been told "We have experienced some issues using silicon brake fluid as it is not hydroscopic & can there for form bubbles in it after prolonged use, so when you press the pedal down there is no effect from the brakes. We use R600+ brake fluid for race use & have had no issues with it at all." (original spelling and terminology preserved).

This does not really make sense to me from the technical point of view (hygrophobic silicone-based fluid does not absorb water and hence makes it impossible for the bubbles to form when heated to acceptable levels, because bubbles are being formed due to boiling water in hygroscopic fluids). I also appreciate I may be wrong somehow and would be grateful for comments from the other people. Thank you in advance.

This exchange is with one of the major Lotus dealers.

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I use Castrol SRF have done on the Exige V6 for a number of years. It is for sure my preference. However I also ensure the fluid is changed at least once a year, typically every eight months, never had an issue and wouldn't change to anything else as its awesome! But you do need to change it at least once a year.

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8 minutes ago, alias23 said:

It is for sure my preference

100% agree, same here - I've been using it from 2011 and will keep using it

9 minutes ago, alias23 said:

But you do need to change it at least once a year

This is an interesting thing. While I do generally just change all the fluids (except for coolant) at least once a year, one could argue that due to no significant difference between dry and wet boiling points for SRF (since it does not absorb water) it does not need to be changed that frequently. The whole logic of changing brake fluid at time and not mileage intervals is due to it absorbing water over time - what is your view on this?

Anyone else has thoughts on the adequacy of reasoning in the first post?

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