Silicone or Synthetic, How to Tell

[theleisure]

Hi there,

I have a '66 Sprite that's new enough to me that I've never had to refill the master cylinder. I'm not sure if this particular car has silicone or synthetic brake fluid. Is there a test I can do to see which fluid I need? I'll have to refill soon, it looks a little low.

Thanks

 

[Morris]

Get a syringe. Pull some fluid from the reservoir into the syringe. Now spray the brake fluid all over your fender. If your paint peels off, it's conventional fluid.

If you don't like that idea, supposedly silicon fluid won't mix with conventional fluid. If you have some conventional fluid lying around the garage you might put it in a glass jar then add some fluid from your reservoir and observe the results. This suggestion is purely theoretical as I have not personally tried it.

 

[sparkydave]

Silicone brake fluid is dyed purple. After a while the dye fades and you're left with a pretty clear, pale fluid. If the fluid is amber or brown, it's not silicone.

 

[theleisure]

Thanks for your help guys. While I was at lunch I dug up the PO's phone number and gave him a call. It ends up that he used Castrol GT LMA. New problem is that that brake fluid is not available in Key West. If I want to fill the reservoir but don't feel like waiting a week for shipping is there another brand of fluid that mixes well with that Castrol GT LMA?

 

[jvandyke]

I think that's a DOT 4 so any DOT 4 off the shelf should be fine.

 

[Brian_James]

I can attest to the fact that silicone will not mix with conventional fluid. Mis them and they will look just like oil and water.

Brian