One application for using a higher temp thermostat is to help reduce emissions, in case your car is marginal and you have a smog test in your area.
O/W stick with the specified one (89C?)

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!