Just a little FYI on DOT 3,4, 4 plus, and DOT 5. Each one has a different boiling point, obiously DOT 5 is the highest. MBs call for DOT 4. The Polo being a VW probably calls for that as well. Most of our domestic cars here in the states call for DOT 3.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member