What DOT brake fluid for 1974 450 SEL?

[franklin]

Hello,
Can someone tell me whether Dot 3, 4 or 5 brake fluid is recommended for my 1974 450 SEL?
Thanks,
Franklin

[Matt L]

DOT-5 is not for street vehicles - do not use it. You can use DOT-4 in applications made for DOT-3, and either of these will be fine. DOT-5.1 is different from DOT-5; I don't know if it's as good for your car as 4 or 5.

[Hatterasguy]

DOT 4 most likely. Pretty much all MB's use DOT 4.

[Jengasan]

I always thought that the higher the spec the better ? So excuse my ignorance but what would be the problem with using DOT 5 or even 6, i.e. the hyper spec'd silicon based stuff ?

[Mike D]

Ya know, back when I was just a young kid, I always thought the "higher the better" ! Oh well, times change.

DOT spec numbers are not indicative of "better". They simply mean different standards. The only difference between 3 and 4 is boiling temps, lower viscousity temperature and a minor difference in water retention value

Do not use a silicone based fluid in a non-silicone system. The silicone based stuff is some slippery stuff and will ooze past all the existing rubber seals.

You could rebuild all the calipers and master cylinder to use silicone but why?

DOT 3 or 4 is perfectly fine AND they can be mixed! Don't try this with DOT 5 or any silicone fluid.

[Jengasan]

see that's what I love about these forums, you learn something new every day

[t walgamuth]

I would use the new synthetic stuff.

The silicone will not leak, I have used it a lot, but it will soften the rubber seals and this is a problem for a mercedes, and I do not recommend using it in one. I have tried and it does not work well.

The silicone is great in a collector us car drum brakes equipped with modern synthetic rubber seals though.

Tom W