[Cp1]

coolant is a very corrosive substance (ethylene and propylene glycol to be exact) and as such are treated with corrosion inhibitors which can dissipate with oxidation and heat. that is why eliminating air or foam from the coolant system is extremely vital, as is replacing/flushing the coolant periodically.

As for the mercedes coolant i dont doubt that guys story, it sounds interesting but mazda TSB E00194 specifically recommends a Green Ethylene-Glycol formula and specifically forbids any other makeup including the propylene-glycol which can is usually dyed red-orange-yellow for identification. so erring on the side of caution i will continue to err with mazda and ford engineers.

And since Ford motorcraft is mazdas consumables manufacturer that is the factory coolant choice.

*also note that for any corrosion test the highest concentration of antifreeze to water should be 70/30. and also keep in mind the coolant seals are compressed slightly which will actually increase their ability to resist any corrosion just like a Paper type waterpump gasket... if exposed directly to liquid it will be destroyed in minutes however it is not uncommon to see them last years in use. just some thoughts in setting up a good test for this.