Synthetic Brake Fluid

[Ed Richardson]

I inadvertently purchased a can of synthetic brake fluid and bled half of the system before I realized the error. The can states that it is compatible with all fluids, but I recall reading that synthetic is not advisable. Comments and suggestions?
Ed

[BobK]

Synthetic DOT 3 or DOT 4 is fine. All I use is synthetic Dot 4. It is the DOT 5 stuff you don't want to get into. That stuff is silicone fluid and it should only be used in a system that was designed for it. Flush your system with synthetic DOT 4 at least every 2 years and you will be fine. I am always amazed at how bad the fluid looks after just a year.

[Ed Richardson]

Thanks for the response. I guess I confused synthetic with silicone.
I do change fluids every two years.
Ed

[Duke2.6]

All brake fluids are "synthetic" since they are made up from synthesized chemicals. The only important issue is the DOT number with 3 and 4 being glycol based and DOT 5 silicone based. The two have some compatibility problems and should not be mixed.

Duke

[Nautilus]

Originally Posted by Duke2.6

The two have some compatibility problems and should not be mixed.

Neither should the DOT3 and DOT4 be mixed, regardless what the label says! Use only pure DOT4, as written on the brake fluid reservoir cap.

I've drained out most of my fluid a few months ago, and completed with Berkebile 2+2 DOT4 brake fluid myself.

~Nautilus

[Duke2.6]

DOT 3 and 4 are fully compatible, but DOT 4 has higher wet and dry boiling point specifications, so mixing the two will reduce the normally higher boiling points for DOT4, which is probably not an issue in normal US driving with bienniel fluid changes.

I always recommend DOT 4, but topping off with DOT 3 will cause no harm.

Duke