Rock Chalk is right that it doesn't matter if the shop is blaming the wrong side because you should replace both sides. For additional logic, be aware that the new strut tops will be a different design from the original.

My shop has put me on notice that my 2002 S 500 will eventually develop this problem as the style of strut used in the first few years of production for these cars will crack and develop a leak.

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02 S500
92 500SL
92 400E (Sold)
87 300E (Sold)
83 300D Turbo (Sold)
75 300D (Sold)
74 240D (Sold after 20 years)