Careful when you start talking about DOT 5. This is silicone and is not compatible with any other brake fluid.

DOT 3, DOT 4, and DOT 5.1 are glycol-based and are compatible with each other. The difference among the three - as I understand it - has to do with dry and wet boiling points, with the higher DOT numbers given to the better performing fluids.

I'm not sure what is DOT 4+. I'm guessing it's a top quality DOT 4. I simply use DOT 4 in my Cabriolet.

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95 E320 Cabriolet, 169K