The owners manual recommends checking the fluid level at operating temperature. The experience many of us have had is that it is sometimes difficult to ascertain whether the fluid is at op temp. So I use the alternative method mentioned in the service manual. With the engine cold, start the car, shift through the gears, and then check the fluid level. It should be about 1/2 inch BELOW the minimum mark.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 160k miles
06 E320 CDI "Rutherford", Black on Tan, 180k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 145k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 79k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife