To maintain cooling system you need 7.5 liters of Red coolant. There is no chance 1992 MX6 engine will work efficiently with bad cooling. Make sure you service system at Mazda with installed 2.5 engine correctly. Before choosing fluid note that engine code KL and volume of 2.5 were installed to your car in 1995. For sufficient use of Mazda MX6 you need to use suitable antifreeze.
So, don’t choose different from Red coolant and obey the number of 7.5 liters. Produced in 1994 the 2.5 engine in MX6 model will serve longer by this. Look at Mazda’s requirements and make your 1995 MX6 serve longer and with no problem. There is an important thing for KL engines of Mazda’s production – they expect good service.