This is just my opinion, and nothing else.
You can find lots of discussion on this subject in the archives on both the e31 and e32 boards.
I did a bunch of research on this a few years ago and found the bulk formulation used by many BMW dealerships could be purchased in 55gal drums from Valvoline. I then ended up calling a couple of engineers at Valvoline, who graciously admitted that Zerex G 05 was “essentially” the same as the “official” blend. It is a low phosphate coolant that is on the Mercedes Benz list.
I do not remember how I got to the “Valvoline” conclusion , but I do remember visiting a couple of dealerships, reading the back of “BMW” coolant containers, a month or so of web sleuthing, reading the back of all the coolant variations at the local parts stores, and calling my friend who was the parts manager for the local dealer in the 90’s. I have a tendency to research the daylights out of something, draw a conclusion and move on. I could be wrong.
I use Zerez G 05 in a 50-50 blend with DISTILLED water.
The previous owner had what I am pretty sure was Prestone green and I flushed and flushed with distilled water one summer week, then each year just drain and refill with the proper 50-50 mix.
My reading a few articles ended up with the conclusion that if you changed pretty much any coolant often (before it ended up having a chance to break down, and then start eating away at our expensive engine cooling systems) you would be OK, but there were compelling reasons to go with low phosphate and low silicate blends. (multiple compelling reasons)
I am not associated with any coolant anything, and I am just sharing MY opinion and experience.
Nothing else.
http://www.valvoline.com/zerex/pdf/Zerex_CoolantChart.pdf
Jack Ramsay
