15Spokes. I just did what you are planning to do. I gave my business to Needswings, Purchased the complete kit to include 5 liters of Mercedes-Benz 236.14, new electrical connector (the original is prone to leak at the "O" rings, a Benz trans filter, new pan gasket and a new plug to replace the cap/plug where you check your fluid with the dipstick. My car had just over 41K miles when I did this. With me it was more time then miles. Needless to say the fluid was not deep cherry red. I really think you are over thinking this on using the 236.14. It is the latest that Mercedes offers and although I've only put a couple hundred miles on her since the drain and fill, I haven't seen any change in how she shifts.

When I did this I first checked the fluid level with the car cold and on a level surface. I checked the trans level with a flexible transmission dipstick (Needswings sells these) noting exactly how far up the fluid was on the stick This way I made sure when I finished adding the fresh fluid I didn't overfill (Checking the fluid again with the car cold) reaching the same spot wet on the dipstick. That's nice that Mercedes-Benz had a drain plug on the pan. My 2013 300C doesn't. Just made the drain that much easier. I let her drain overnight then proceeded next morning to drop the pan allowing the additional fluid to drain out. Cleaned the pan and magnet in my parts washer using mineral spirits. Replaced the electrical connector, trans filter and pan gasket torquing the pan bolts to factory specs.

Here's some pics of the fluid used and the kit Needswings sells. Although I purchased 5 liters, I only drained and filled 3.6 liters of fluid. Good luck on your decision but again I think you will be OK with the 236.14.

Regards,