He seems pretty knowledgeable to be honest, at least by the standard there is here

__________________
Smoke Silver 1994 E220 Coupe Automatic
0 kilometers 6 September 1994
100,635 kilometers - 6 September 2010

Just buy one more bottle (1.5 litres) and give him all 3.

4.5 litres of MB cooland in an 8.5 Litre system will give you an approximately 53/47 mix of coolant/water. Close enough for the 50/50 mixture you're looking for. Then, buy one more bottle of coolant, save an empty bottle and make up your own 2 litres of 50/50 mixture for your over-flow reservoir and occasional top-offs.

This isn't a science project...it's an everyday thing...

__________________

M. G. Burg
'10 - Dakota SXT - Daily Ride / ≈ 172.5K
.'76 - 450SLC - 107.024.12 / < .89.20 K
..'77 - 280E - 123.033.12 / > 128.20 K
...'67 - El Camino - 283ci / > 207.00 K
....'75 - Yamaha - 650XS / < 21.00 K
.....'87 - G20 Sportvan / > 206.00 K
......'85 - 4WINNS 160 I.O. / 140hp
.......'74 - Honda CT70 / Real 125
.
“I didn’t really say everything I said.”
. . . . . . . . . . . . . . . . . . ~ Yogi Berra ~

True, it's not going to make a whole lot of difference if the mix isn't exactly 1:1. Still, if it were me, I'd make sure that the mix was, if anything, slightly less coolant than water, rather than the other way 'round. Better cooling properties for a hot climate with slightly less coolant-to-water. Still, nothing dramatic will occur if you follow mgburg's advice and put in all 3 jugs of coolant and end up at 53:47. I would just rather have the ratio the other way.

__________________
1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't