Its a 23.8 gallon tank, unique to the diesel 124 of 1995 only. All others, gas and diesel, had the run of the mill 18.5.

I might add, the 500E had the 23.8 gallon tank as well...

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93 300D 2.5 Turbo, Black/Palomino 273K
09 E350 Black/Black 41K