You can use Dexron III Mercon Tranny Fluid (non-synthetic type) or Mobil 1 Synthetic ATF, either will work fine, Synthetic is about 3 times as expensive as Dexron but its worth it. (I switched to it and it made quite a difference in smoothness and overall performance....)

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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)