I will go out on a limb and say that by the time you find out what the coolant specs are for your Trib and find a non-Mazda supplier, you might as well buy it from the Mazda parts counter. I would not go with a so-called universal coolant. It is hard to find specific coolants outside of dealerships because the mass market auto parts stores do not want to devote the shelf space. The same goes for repair shops. Heck, we have seen evidence that even dealers don?t use them. Start with your owner manual and see if it lists a specific recommendation. Then you can check with the manufacturers and see if it is an approved product for that specification.
An over-simplified coolant history goes like this. Old green was high in silicates which tend to precipitate and gel if not replaced frequently. This clogs and erodes the cooling system. They are used because they coat the metal, in place of metal oxides (rust), and prevent the corrosion. Phosphates were also big as they also inhibit corrosion and buffer the pH. The trouble with phosphates is that in hard water they also precipitate and sand-blast the cooling system. Japanese engineers don?t line silicates and euros do not like phosphates. (I have been told that is because euro water tends to be hard.) The fact is that the stuff worked fine if you changed it frequently and used good water. The trouble is that the average car owner can?t be trusted to maintain a vehicle and the use of purified water in a cooling system is beyond the reach of many people as well. Oh, silicates and phosphates are cheap and cheaper, but they are fast-acting.
Beyond freeze and boil protection, two important things that coolant additives do are coating the metal with something before it can oxidize, and buffer the pH to keep it neutral or slightly alkaline as the breakdown of ethylene glycol tends to make it acidic.
Some people would prefer to continue using the old-fashioned green coolant in their iron engines with soldered copper radiators. It is impossible to find as far as I can see. Now all coolant is low in silicates even the stuff that is supposed to be old-fashioned green.
OAT (Dexcool) might or might not have other problems depending on who you ask, but it has no silicates or phosphate. Note that Toyota's version has some phosphate. The organic acids are slow-acting corrosion inhibitors meaning that they take longer to coat the metal.
HOAT (G05) uses different organic acids and has some silicate to do quick repair on any bare metal. Note that Ford specifies silicates in its yellow G05 coolant. Fortunately for me in this issue, my car and my wife?s are both FoMoCO vehicles and can use G05 that is readily available outside of dealerships, though not as readily available as the universal stuff.
As far as I know, Zerex and, maybe Peak, are about the only major aftermarket suppliers that sell coolants made to several specs. There is lots of information on their web sites. It is worth seeking their products out if you don't want to get stealership stuff. I would go with them rather than some universal, one spec. fits none, garbage. They still make a "traditional" green. You need that with copper/brass soldered rads. There are other greens, but their old-fashioned stuff has plenty of silicate and phosphate. Last time I looked, both companies had a lot of information about coolants on their web sites with Zerex being better. Recently it was pointed out to me that there is a pretty good coolant forum here: http://www.bobistheoilguy.com/forums/ubbthreads.php. Note that that Zerex chart is does not well mirror Ford?s found at the Motorcraft web site. It leaves out some detail. It looks like Zerex might have dropped a couple of formulations recently.
You might run across borates and nitrates as corrosion inhibitors. That is more slanted to heavy-duty diesel, I believe. I think that these are slipping into disuse as well. If you diesel guys want to dispute that, fine. Do it and then go discuss it in an heavy-duty diesel forum HD diesels need anti-cavitation additives as well.