Interesting....that light does not work (as far as I know) on ANY of our MBs.....it comes on when starting the car on a couple of them, but does not go on for low fuel warning....maybe it does on the 300E...haven't run it quite low enough yet.....I've come close to R but never actually laid the needle down....
On a side note, your dash has some pretty severe scars from prying out the cluster!! 
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-diesel is not just a fuel, its a way of life- 
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)
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