I've noticed as a rough guide that chassis capacities seem to be very similar and in many cases identical across the board. Witness the W126 (like yours) which takes 48 oz. R12 and 7.75 oz. mineral oil for both the 560SEL and 420SEL. I have a 380SE and recall reading somewhere in this forum that the capacity is 48 oz. and I used that figure in calculating my R134a charge over the weekend. It's just nice seeing printed confirmation.

EDIT: I did a typo - the actual capacity is 46 oz. or 2.875 pounds.

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280