I absently-mindedly left the key in the ignition of my 99 E300 (not sure whether position 1 or 2 but the climate control was definitely off) for about eight hours and was surprised to find the battery essentially drained when I tried to start it. What would drain the battery in that period of time?

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 159k miles
06 E320 CDI "Rutherford", Black on Tan, 178k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 145k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 75k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife