brake fluid choices

[Ferrolanoman]

Gents,
I'm about to replace the brake pads and bleed the system on my 1970 280SL. On hand I have three unopened containers: ATE Dot 4 Super Blue Racing, CASTROL Dot 4, and NAPA Dot 3. Will all of these work? Is one better than the others? Will any of them harm/disolve any rubber parts (hoses, caliper seals) on my car? Are they all compatible with the present fluid in the system--which is not synthetic?
Thank you for your advice.
Happy Easter to everyone in these troubled times. Stay safe, stay home, stay well.
Ricardo.

[wwheeler]

Dot 4 is typically better than DOT 3 and has a higher boiling point. I know you can use DOT 4 where there was DOT 3, but not sure if you can go from DOT 4 back to DOT 3. I would use the DOT 4. 

The ATE blue must be older because it has been outlawed (at least in the US) for years. Brake fluid cannot be blue in the US and not sure if it is still available in the rest of the world. Most would switch from blue to amber when doing brake flushes as it was easy to know when the old fluid was out and the new fluid had made its way through the lines.

[Aaron h]

Wallace, do you or anyone know why the blue brake fluid was outlawed in the U.S.?  I really miss using it for the ease of knowing when the old fluid was out. 

[MikeSimon]

Both DOT3 and DOT4 are totally compatible. You can exchange back and forth. Like Wallace said, the only difference is that DOT4 has a higher boiling point. You can even mix with DOT5a, which is also non-synthetic. Do not mix with DOT5!

[Ferrolanoman]

Thank you all for your replies. I had bought two containers of the blue fluid (Pelican Parts) when working on my '86 911 Carrera about 8 years ago but only used one can. It's been on the shelf, sealed and unused since then. I would think that it is still good but if I don't use it now I'll probably take it to our local hazardous recycling center. Given the comments thus far, I'm inclined to consider the CASTROL 4-dot the safest choice. The job I'm embarking on entails replacing the pads on all four wheels--hope it turns out to be as straight forward as it sounds.

[Jonny B]

Did a search on the net. It appears the only reason the blue fluid was banned, was because it was blue! The US regs state that brake fluid must be clear or amber. That way it is not mistaken for other car fluids and hence used in the wrong place. Not sure what that a would be, but that is what I could find. There is no performance or other inherent reason.

Goofy as all get out.

[doitwright]

Thank you all for your replies. I had bought two containers of the blue fluid (Pelican Parts) when working on my '86 911 Carrera about 8 years ago but only used one can. It's been on the shelf, sealed and unused since then. I would think that it is still good but if I don't use it now I'll probably take it to our local hazardous recycling center. Given the comments thus far, I'm inclined to consider the CASTROL 4-dot the safest choice. The job I'm embarking on entails replacing the pads on all four wheels--hope it turns out to be as straight forward as it sounds.

If you choose to not use or want the blue fluid, I would be glad to buy it from you.

[wwheeler]

Yep, that is right. Only because it is blue. Unbelievable. If one doesn’t know better and has to rely on the color of the fluid to know where to put it, that is indeed a sad state. Let’s hope that person doesn’t work on his own car.

[Jonny B]

Wallace, you sure have that one right!

[Ferrolanoman]

No need, if i don't use it you can just pay for shipping to your house.

[MikeSimon]

As long as the container has never been opened, the fluid is O.K. Glycol based brake fluids are hygroscopic and attract moisture from the atmosphere  which settles in the fluid and spoil it.

[perry113]

I am going to throw out what I have done on all my vintage cars including 4 Mercedes.
When I rebuilt the braking systems I installed DOT5 silicone fluid.
The entire hydraulic systems were completely rebuilt prior to this.
No moisture problem with DOT5 and it does not damage painted surfaces.
I am now running it in my 1966 230SL 4 speed and am using it for the clutch system.
Been running it in my 1965 230SL automagic and has had tremendous luck.
Just a DOT5 perspective

[ja17]

Dot 5 silicone brake fluid can harm some rubber components in very early Mercedes brake systems. Using it in a 190SL was always fatal to the hydraulic brake light switch. Since the Pagoda came later, it might work fine? 

[MikeSimon]

If you have a virgin new brake system with new lines, mc and calipers, DOT5 is O.K. and has quite some advantages, especially for a car that is hardly driven. If there are ANY remnants of DOT3 or DOT4 DO NOT use DOT5. The fluids do not like each other and the liquid mix will coagulate.
Also, as DOT5 does not "absorb" moisture, this moisture, which WILL BE in the system, will accumulate in the lowest points of the system and will cause corrosion there.
Special care has to be taken when filling with DOT5, DO NOT shake the bottle and pour very carefully. Agitation of the fluid will attract moisture, which will then "fall out" when the fluid settles.
Pros and Cons. For a car that is regularly moved and regularly maintained, I.e.: brake fluid changed every two years, I would recommend not to use DOT5, just because the seal issues, as Joe mentioned, may be a concern.
Also, if you are a spirited driver and like to "brake late", you will find that DOT5 produces a slightly "spongier" feel on the pedal.

[doitwright]

No need, if i don't use it you can just pay for shipping to your house.

Send me an email if you wish to let it go.

[UJJ]

I rebuild my brake system 5 years ago. New Master, new calipers and new hoses.
I used DOT 5 silicone after that.
I have not seen any problems since then.
Best, Urban