brake fluid question

I replaced my master cylinder last year. On the cover it says use d.o.t 4 brake fluid. All I can find is synthinec. Is this o.k. to use? The bike is an 81 xj550h.

 

Dot 5 is a stand alone brake fluid. It cannot be introduced into a system that has had dot 3 or 4 in it. It will attack and deteriorate the rubber parts. So make sure it is dot 4 or 3 for your system.

 

the brake fluid I have is not 5 that is silicone based. But this is synthenic. I was told by the guy at auto zone it would most likely be ok but he is a guy from auto zone. I figured somebody here would know better.

 

I'm planning on flushing the system.

 

I wouldn't mix synthetic with regular brake fluid as most are not compatable.

If you go with the synthetic I would recommend draining and flushing first.

 

Ok Sorry, I misunderstood your original post. Dot 4 is a synthetic that has a higher boiling point. So synthetic is ok as long as it is dot 4. I was afraid you meant dot 5 which is a bad thing in a dot 3 or 4 system. It just can't be introduced even if you flush the system. Follow Richard's advice and your set.

 

I flushed out the system and it is now filled with the #4 synthetic fluid. All seems fine. The reason I needed to it flush out is after only a year the fluid in the window was the color of apple cider. I think the lines are original equiptment so it's time to replace them. I ordered a stainless steel line today that should fix it. Thanks a lot for the advice.

 

The brake lines are most likley original. You will love the stainless braided lines. More solid brake lever and more stopping power. Glad to hear all is well. Have fun with that XJ now!

 

There's also the Dot 5.1. Is similar to Dot 4 (not silicon based) but has a higher boiling point and better properties to moisture.

 

Just an update. I installed the stainless steel line, vast improvement. I also read on the brake fluid bottle that this ( #4, valvoline synthetic) is compatible with regular brake fluid. Thanks agaian.