Yes it will. It works properly with any glycol based fluid. The MB fluid may have have a slightly different formulation that some other fluids, but it is still glycol based and thus the prestone antifreeze tester will work correctly.

If you have one, use it and see what it says.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record