The correct bulb wattage is embossed on the taillight housing.

For replacements, use bulbs with the nickel-plated base (Osram, Philips, Sylvania). Stay away from the gold-anodized ones, as they show a different resistance to the circuit, which could potentially set off the dash indicator...

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car