Which brake fluid?

[gianton]

Hi,
what if FUCH as major oil distributor gives wrong advice?
I was told (internet information) that DOT4 and DOT are of tottaly different composition and incompatible.

I trust FUCHS for more than 40 years in all my cars. Never had an issue. So I trust their lubricants search site.

 

[alexanderfoti]

Thanks.

will DOT 5.1 in the brake system cause damage or brake malfunction?

No. It will be fine

 

[Woodleigh]

I trust FUCHS for more than 40 years in all my cars. Never had an issue. So I trust their lubricants search site.

Agreed, Mercedes uses Fuchs lubricants & fluids as their factory fill.

 

[w204benz]

will DOT 5.1 in the brake system cause damage or brake malfunction?

DOT 5 is the one to avoid, completely incompatible.
DOT 5.1 is a better version of DOT 4, in fact the specs are very similar to MB DOT 4+. The only downside I am aware of is that it absorbs moisture a bit more readily, so you may need to flush it more often.

 

[alexanderfoti]

It is true that Dot 5.1 is a better version of dot 4, with a higher boiling point

DOT 4 has a max viscocity rating allowed of 1800 mm²/s
DOT 4 ESP (DOT 4+) has a max viscocity rating allowed of 750 mm²/s
DOT 5.1 has a max viscocity rating allowed of 900 mm²/s
DOT 5.1 ESP (DOT 5.1+) has a max viscocity rating allowed of 750 mm²/s

Aside from other differences and boiling point differences, the main reason for these additional specs is lower viscoscity for ESP etc.

DOT 5.1 in a DOT 4.1 has a close viscoscity rating and will be unlikely to cause any major issues.

DOT 5.1+ can be used in a DOT 4+ system with all the benefits of a higher boiling point etc. It just isnt the spec defined by MB (even though its better)