Make sure you service system at Mazda with installed 1.8 engine correctly. Only Red antifreeze type is suitable and you’ll need 7.5 liters of it. Only exact type of antifreeze will suit Mazda 6 cooling system. Before choosing fluid note that engine code LF17 and volume of 2.0 were installed to your car in 2002. There is no chance 2005 6 engine will work efficiently with bad cooling.
Produced in 2013 the 2.2 engine in 6 model will serve longer by this. To endure car life take only Red antifreeze and pour not more or less than 7.5 liters. It will be advantageous to follow Mazda’s rules for 2006 6 service. A lot of L813 motors are used long in Mazda cars but only with good service.