it doesn't matter what brand you use. in the summer you could settle for watter if your cheap, but make sure you swap it with anti freeze before it gets to cold or you'll have a load of problems. you can find a 50/50 mix at most gas stations.
Dexcool
You should use a 50/50 blend of a good commercial antifreeze that is sold everywhere!
DEX-cool is a coolant made specifically for Pontiac Grand Ams. It has certain amounts of lubricant and detergents made just for this engine.
134a
DEXCOOL OR LONG LIFE,IF ITS NOT PREMIXED BE SUR TO MIX IT,60% COOLANT 40% WATER.
10w30
A 1994 Mercury Grand Marquis would have come from the factory with a 50 / 50 mix of distilled water and GREEN color antifreeze ( meeting Ford specification ESE-M97B44-A )
The regular universal green coolant.
Red, 5 year, HOAT type.
For a 1994 Cadillac Eldorado, you should use a high-quality ethylene glycol-based coolant that meets the GM specification, preferably the Dex-Cool type. It's important to avoid mixing different types of coolant, as this can lead to system issues. Always check the owner's manual for specific recommendations and ensure that the coolant is mixed with distilled water if it's concentrated.
R134a
Any HOAT coolant will work. Zerex G-05 coolant is good too. Don't use anything else.