Zerex G5 is the AF most often recommended here for MB.   I believe the
Zerex container actually says it is used by MB for their new cars.
I've heard the important diff is that this AF maintains better control
over the PH.

Walter, I believe Mercedes uses it's own coolant that is quite good. It
looks clear like water it may be worth paying a little more. I think
keeping like brand anti freeze is the best for the engine if you are
doing a radiator dump and refill. I'm not being fimiliar with where the
radiator petcock is on the ML.  I would buy 1gal of MB coolant and make
a 50% mix , you then have two gallons. Being that you are not draining
the engine block, plan on this procedure on a yearly basis. Drain the
radiator, then refill it letting the engine warm up temp in driveway to
make shure there are not any air pockets in cooling system,  drive on
short road test, add coolant if nessary.
This is one shade tree opinion.

I don't know if this is true for your MBZ (it is for mine, but it's 28 yrs
old):

Check to see if you need to vent the system when replacing the coolant.

In the past, you would follow the hose at the top of the radiator back to
the engine block. There, you'd see that it was connected to a unit called
the thermostat housing cover. On the top of this cover was a plug/screw.
It was the highest point in the cooling system.

You would unscrew this plug, take off the radiator cap, drain the coolant
out from the bottom of the radiator, close the drain of the radiator, pour
the new coolant into the radiator until it started coming out of the top
of the thermostat cover, screw the plug back in, put the radiator cap back
on, and fire up the engine.

Typically, the water temperature would rise up and then, well before
red-lining, drop down to it's normal operating temperature. If it
red-lined then either the thermostat didn't open up (and needs to be
replaced) or there was air in the lines (meaning you didn't vent the
engine block properly).

Replacing the coolant is something anyone should be able to do. Not
venting the system when one has to is the only problem I can think of (of
course, others in this newsgroup will soon enlighten me about the ones
that I've missed).

You shouldn't have any trouble.

ron