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.

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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