Dot 5 Brake Fluid?

Just throwing this up for discussion..Is dot 5 fluid really worth installing?. I have heard that it is a good idea to use this in a car that is not driven that often. It has the ability to resist moisture build up. Also there is 5.1 fluid. What do you think?


Well Known Member
Ive swapped out dot 5 for dot 3 and 4 for years on motorcycles and never had a problem. Using a brake bleeder to suck all the old fluid out is best way so it doesnt keep mixing as you try to bleed pedal method. Dot 5 has never created seal or hose destruction issues on any bikes. Some swaps go back 30 years.


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Supporting Member 2
The differences are glycol based versus silicone, boiling points, compressibility, and if they are hydroscopic ( absorb water ) I have always thought that Dot 5 was originally invented towards things like the military where they knew moisture was an issue. Then there is performance, and some say that Dot 3 and 4 are better performing due to resisting heat better. I have seen one bike that the rear brake line was routed too close to the exhaust and the fluid failed ( my neighbors wife's bike when we were riding ) Changed the fluid and moved the line slightly and no problem. However, like Wristpin said, I have not seen any corrosion or hose destruction. That's the good part of Dot 5, and your paint.

1958 delivery

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Supporting Member 2
DOT 5.1 is not silicone based as 5.0 is. 5.1 is same as 4 just has higher boiling temp
DOT 5 is silicone based and has higher boiling temp then DOT 4
DOT 5.1 HAS highest boiling temp of all


Well Known Member
I put DOT 5 in my Corvette back in 1990 and have not touched the brakes since. Before that every time I wanted to drive it I had to work on the brakes as one or more of the calipers was leaking. Corvettes have 4 piston calipers at all 4 corners and they are a real pain in the A$$ to fix. I got SS sleeved calipers rebuilt the master cylinder flushed out all the brake lines and put in the DOT 5. The brake pedal is a little spongy compared to the DOT 3 due to the compression properties of the DOT 5 (my car has manual brakes) but its worth it as I am not road racing my car and I never worked on the brakes since.